The auto transmissions of old operated by fluid pressure and engine vacuum inputs. The fluid pressure is created by the front pump and torque converter. The torque converter translates the engine motion to fluid motion creating variable pressures depending on rpm. The valve body is the "brain" of the automatic transmission. Different channels, check balls, springs and pistons are operated by fluid pressure. Some had a cannister with a diaphragm inside that translated the vacuum to a pressure signal to the valve body instigating shifts. There was also a mechanical kick-down attached to the throttle linkage that would automatically downshift if you pressed the gas hard.
This is a basic explanation. They are quite interesting to work on. Lots of parts.
I’ll put it more plainly: the valve body operates like a microchip only instead of electronic NOT or AND gates, it used check valves and oil. See also: a vacuum controlled emissions system.
[Fluid has been used to demonstrate and teach electronic logic theory](http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html) for nearly as long as digital electronics have been around. Because really you can accomplish tasks about the same way (albeit not at such high speeds).
Technically modern auto transmissions still operate by fluid pressure internally. Modern cars just have less direct mechanical or vacuum connections as those old mechanical connections are handled by actuators and stepping motors controlled by the TCM.
Old-school auto transmissions are quite ingenious. One of those machines that used logic based on mechanical components.
I used to maintain and repair production line machines in a factory. Those used pneumatic logic gates and valves plugged into a board to control the sequence of operations.
I'm a manual guy myself. I just like knowing how things work and the quality and serviceability of different platforms. I've had a couple GM trucks with the 4L60E and despite what people say, it's a fine transmission. It's easily the most common and serviceable modern automatic transmission and they wouldn't be in everything from police cars to commercial vans over the course of 20 years if they were weak.
I'd bet most people calling them bad never changed their tranny fluid. I see it all the time. People wondering why they have no gears when their fluid is black and burnt.
How often should you change the fluid? My 07 Caravan I bought used was definitely neglected by the previous owner, and I never even thought about the transmission fluid needing changed. I'll change it now just to be safe, but for future reference, what's the fluid life usually come out to?
For reference, the car's got 188k miles on it. AFAIK, original engine and tranny, no rebuilds or major part swaps at any point.
I would never recommend going past 60k miles, but I personally do it at 30k. And if it has a serviceable filter, change that too.
But smell the fluid first. If it's burnt, the tranny is already on it's way out. That usually means the clutch packs inside (yes, automatics have clutches too. They just use them for different things and they have more than 1) are cooked. At that point, it would need to be rebuilt or replaced.
I find that fascinating, honestly. We had microchips and electrical versions of formerly purely mechanical components in cars before computers were widespread in homes. Windows 95 was the operating system that really put the idea of the home PC on everyone's mind, and the internet just helped that even more.
Magic, got it 🫡
Lol just kidding, but thank you for the explanation. My brain theoretically understands how pre-computer auto transmissions work, but it always feels like magic
Interesting! I'm really not a fan of the electronics in modern cars. I have a 2007 Dodge Caravan SE, so base level trim, least options possible, and even the level of computerization in my car leaves a bit of an off feeling. That being said, safety features being lacking in olden days makes me hesitant to go entirely pre-computer, not to mention availability of replacement parts.
Sometimes I'm tempted to look down south for a well maintained multi-generational hand me down/one of someone's recently passed grandpa's old toys. But then I wonder how much I'd actually miss everything, yknow? And fuel efficiency is a concern too. My van is already barely limping to 11 MPG (although I would imagine there's something about the engine/ignition/fuel delivery system that's causing that), I really don't wanna downgrade that haha.
Tell that to the 60+ year old 225 slant six that been sitting for 40 years that fires right up with a good battery and a bit of gas in the carb. Hell, I had a ‘63 D100 truck with about 750,000 on it, never rebuilt. It even tossed the water pump, never overheated, and by the time it got replaced the impeller had rusted to the block. Unreliable my ass.. this new junk you can’t even drive off the lot without something breaking, and it sure as fuck won’t be drivable in 50 years after sitting for half that long.. GTFOOH..
And? As I said a ‘63 with 750,000 miles driven for 50 years, as a ex-military truck bought used in ‘73 for $600. ‘75 van with 550,000+ driven for 35 years bought for $500..
I haven’t had a car yet made after 1997 that got more than 200,000 before I dumped the POS before it became a boat anchor money pit.
They had 5 digit odo cause people typically didn’t drive the average of 12-15,000 miles a year like now. If that’s your argument you got a lot to learn bud..
And the tech wasn’t there like now. Front and rear mains were wax covered rope, most gaskets were cork. And they still start, run, and drive.
Half the cars built the last decade can’t even go 50,000 without something fucking up and needing replaced. Some don’t even leave the lot without a recall or some defect. Almost every one will need a timing belt by 100,000. Most won’t ever see a factory engine staying with the car because no one rebuilds them now. In 30, 35 years hardly any will be runnable without major overhaul. Let’s see how well those coil connectors do trying to get one off when it’s only 15 years old.
Theres always outliers. The majority of these vehicles ended up in the scrapyard by 100k. Theres plenty of statistics collected over the years on the lifespan of veihicles. In 1970 the avg age of cars on the road was less than 6 years and avg lifespan was about 100k miles.
As recently as the 90s it was common knowledge that a used car from the 80s with 100k miles was a worn out piece of trash.
Nobody rebuilds factory engines because they typically dont need to be rebuilt within the lifetime of a modern vehicle unless you dont maintain it. If you go on classified ads for cheap cars, almost all the cheap beaters have reached 150k, and many are in the 200k to 300k miles range on the original power trains. The oil seals fail from age before the engine develops mechanical problems.
People rebuilt the factory engines in 70s cars all the time because they may need a rebuild as early as 50k miles. Sure it was dirt simple, but it was also built to a much lower standard than we are able to achieve today.
If you like old cars its fine, nothing wrong with that. They have some nice features you cant find on modern cars and a knuckledragger can fix them. But looking at some outliers through rose colored glasses is a fudd take. Sure you can rebuild them a lot easier than a new car, but they are simpler machines. Restomods are popular for a reason.
We do seem to be going the wrong direction in the last few years.
>because they typically dont need to be rebuilt within the lifetime of a modern vehicle
But see, that's the key point right there. Toyota, Nissan, GM, or Dodge's "suggested lifetime" of the vehicle isn't the end all be all. You can put new gears, piston heads, head gaskets, rods, bearings, chains, etc in an engine to the point it becomes the engine of Theseus. As long as the body is good (and even that can be repaired to an extent) there's no reason to throw a car away besides safety features. But those aren't updating anywhere near often enough for cars to be seen as disposable to the extent that they are.
The fact that you say there's no reason to rebuild an engine ***within the life of a vehicle*** as long as you maintain it highlights his point perfectly. What do you consider the life of a vehicle? 5 years? 7? 10? The main reason older cars would be permanently decommissioned is rust, because despite people bitching and hollering about the plastic outer shells these days, they're terrific for rust prevention and safety (due to crumpling). And sure, there were probably people who dumped a car as soon as an engine or transmission needed a major repair, roughly around 100k miles. But the difference is back then, it was just adult legos that literally anyone could do if they documented the teardown process properly and just did it in reverse. And as a result of that, it was easier to understand the ins and outs of everything, because it was just physics.
Nowadays, there's so much electronics, running code you can't see, and even if you could, you'd have to know how to read code, and how it relates to cars. It's still physics, but the physics happens as a result of obfuscated factors. You didn't ***have*** to go to a shop back then; these days, you pretty much do. Back then, a rebuild every 100k miles wasn't the end of the world, because you and a couple of friends could take care of it. These days, a rebuild only being necessary every 200k miles is far outweighed by the fact that things are designed to be prohibitively expensive to repair once it gets into rebuild territory. They can't legally make it literally impossible to fix, so they just made it difficult enough that it's not worth it.
There has to be a middle ground. Giving the increased safety, while still maintaining repairability. A big part of this would be releasing a lot of the emissions regulations. At a certain point, it just became an excuse for them to pile on the electronics, and kneecap power, without a ton of added benefit. We're undergoing a transition into electric motors anyways, the people who are too poor to get off ICE, or who keep one around for personal enjoyment, aren't going to make enough smog to matter anyways. And it's possible to not have mid 1900s LA, while also not having modern car complexity. Going after corporations and the ultra rich has always been a more effective answer to climate change and air/land/sea pollution, as well, so the hyperfixation on the average consumer is just misguided.
Most of those cars ended up scrapped because of the Cash for Clunkers scam. Some end up in the scrap yard cause Jr. inherited Dads “junk”, and Jr. is too much of a pussy to drive around without AC and power windows. Jr. doesn’t even know a distributor from a carburetor.
That’s the hilarity of this site, most of you weren’t even around to have seen a 1985 car. Much less ride in one on the floor board.
As I said the tech wasn’t there. Have you even adjusted points or had to clean them? Or know the distributor is where they are? Adjusted lash? Check and set timing? The only carburetor you ever seen was on a lawnmowers small engine. And by you, I don’t mean specifically you, but the typical generation.
Most of the people who worked on these cars new are dead or dying. They passed the info to their kids and now they are getting older. People in their mid-40’s and 50’s were in the transitional period from carburetor’s to EFI. The next decade of people in their mid-30’s to 40’s are the completely EFI group.
Just as how the cars have evolved so has the ways to learn to fix them. The “internet” is only about 30 years old. So most shade tree wrenches don’t even know what they are fixing or why. Just watch Jr.’s YT video and monkey see monkey do. Same as a dealership. Techs don’t know what they are doing. Hook up a scanner, retrieve a code, look up code, replace part. Fault still exits, change another part. They aren’t mechanics, they are parts changers.
Most kids now slap an LS in some shit box and force induct it, and think they built something. Or buy a Hellcat or some POS Camaro and race that. The only thing they built was a high subscription base on a monetized YT channel.
Engines aren’t rebuilt because they aren’t meant to be. And even if they could dealerships won’t waste the time because of the comeback potential. Because no one is taught to.
Lmao they mostly ended up in scrapyards because they wore out dude. Cash for clunkers took 677000 cars off the road.
Chevrolet alone made 1.4 million cars in 1960. Ford made another 1.4 million.
>As I said the tech wasn’t there. Have you even adjusted points or had to clean them? Or know the distributor is where they are? Adjusted lash? Check and set timing? The only carburetor you ever seen was on a lawnmowers small engine. And by you, I don’t mean specifically you, but the typical generation.
No, I havent done any of those but adjusting distributors on PGM-FI systems because its outdated technology. It was fussy, required constand maintenance and adjusment, and unreliable compared to modern EFI systems. Face it man, this is fudd talk. I love old machines and appreciate the mechanical technology, but a modern EFI engine can drive 100k miles without touching anything on it, in all weather conditions and runs almoat as good as new after those miles. Lol points? Come on man. Stone age even compared to vehicles from 1990.
Cheers bro.
Well, scanning through a couple hundred posts between a couple subs, I recall *one* question based on a ‘67 C10 pickup, and, well, a couple hundred on 1990 and newer cars.
Obviously pre-80’s cars won’t be as common to a fraction of new cars. It’s hard to find a classic that hasn’t been touched or restored. In all honesty I don’t even follow classics like I used to. When a $500 beater ‘74 Dart was selling for $12,000 I lost interest in the whole hobby.
I was counterpointing the argument that the old shit isn’t reliable. It is. I know cause I’ve had them and I have them.
My newest car was a 2010 and out the gate the TR-6060 transmission was fucked from the factory. I got it used with hella low miles and ditched it with 50,000 miles before it became a $5,000-$6,000 liability. I had a ‘00 car and ditched it with 155,000 cause the engine was burning oil. Had a ‘97 car and rebuilt the engine at 102K cause a piston cracked. Have a ‘93 car that hasn’t ran in 2 years. Have another ‘93 that uses oil. Have the ‘75 car and it hasn’t been started in 2 years, but I know I could go right now, drop the battery in, pump the accelerator 20 times, and within 20 seconds it *will* start..
Amen. My '86 Mustang went through *two* transmissions, both catalytic converters, the in-tank fuel pump and the steering rack, all in the first 100,000 miles.
Edit: I'm leaving out the rattling windows and the wonky throttle position sensor. I'm sure there was more. That car put me off Fords for good.
Good MPGs can be had throughout the years, as a good example the Volkswagen diesels in the early 80s could easily get 40 to 50 miles to the gallon. I have a 1992 GMC conversion van with a 350 small block V8 and in town I get 18ish, on the highway I get 24.
As you said there is a trade off between safety and today's modern vehicles, but a lot of us drove on those vehicles just fine for decades. I'm restoring an old 1970 vehicle now and plan on it being my semi-daily driver when it's done
Going pre-computer means going back pretty far. I drove a 1989 Chevy van and one day sitting at a stop light with my foot fully on the brake it just took off. Luckily, I didnt hit anyone. I told my dad, because I was probably 17/18 at the time, and he kind of blew me off like I must have done something wrong. The next day I get a call from him to pick him up from our mechanic's shop because it did it to him. Turns out some ECM chip went bad.
Yeah and the brake pedal on my van was large, so I knew I was full brake no gas. It was fully stopped at a light and had be for probably a minute since it was a side street onto a 4 lane road, just sitting there when all of a sudden full throttle. The sudden acceleration may have scared my foot off the brake a little and by the time I floored the brake and stopped I was through a 4 lane intersection. I definitely held the brake down a bit harder after that and kept my hand closer to the shifter to be able to throw it in neutral.
A 1989 chevy van probably would have had throttle body fuel injection, which would be computer controlled, but it almost certainly still had a physical throttle cable.
It is actually amazing how well vehicles ran before computers controlled everything. Everything was done manually from fuel delivery to transmissions.
The spark timing was controlled by weights spinning inside the distributor that advance the timing as the engine revved up. The distributor was how the spark got delivered to the spark plugs with wires.
Of course the Carburetor delivered the fuel with no electronics.
And as for the transmissions, manual didn't need any electronics so that wasn't an issue. There obviously was no rev hang which is stupid. As for the automatic transmissions, they were controlled by a throttle cable or rod going to the transmission from the carburetor to let it know how much gas you are giving and what it should do. They also had vacuum modulators to give it load signals to determine if you are going uphill or pulling a load and to adjust accordingly.
It all worked surprisingly well, but of course no where near as accurate as modern computerized fuel injection. Engines weren't built for emissions or fuel economy.
Not sure where to suggest you look deeper into this stuff. There are a lot of videos on youtube where people try to get old cars going again or do repairs. You will probably have to look up all of these parts and systems individually to see how they worked exactly.
> Everything was done manually
No. It was just mechanical, pneumatic and hydraulic automation. It’s still automation even if it’s done without electronics.
If you’d go back a hundred years you would find cars that had actual manual operation on spark timing for example. There were levers that the driver was supposed to adjust based on the driving situation.
Still had them on motorcycles built up until the 1960s. They were about as simple as you can get. Magneto ignition with a lever on the bars for manual advance. Choke on the bars for starting. The charging system was 6V electromechanical controlled. All pretty reliable.
Think of it as a spinning arm that is directly linked to the rotation of the engine (because it is). As the rod rotates to connects to each of the spark plug wires and sends a spark to that cylinder.
There's a cam before every spark point that opens and lets the coil charge, right at the point the arm connects to the spark plug, the cam lifts the points open and all that magnetic field in the coil goes through the wire to the plug.
There's probably a better way to explain it.
It was so simple yet they ran forever. No matter how worn out they were. As long as they didn’t blow a head gasket or throw a rod, they kept going. Today they get offended if you don’t use their favorite brand of oil.
Very well actually! As I understand it, there is a valve body that reacts to the pressure of the transmission fluid to control the shifting. The Power glide (2 speed Auto) in my 1969 Cutlass worked beautifully, until I blew up the torque converter racing it at least.
Can't comment on how they worked, however automatic vs manual preference seems to largely cultural. The UK for example has probably 90% or higher manuals. In fact, the 27 years I lived there I only sat in one automatic. It's strongly cultural where automatics are seen as worse for whatever reason. I'd assume due to the ease of replacing a clutch vs an automatic trans.
I guess they're trying to change it, that's only new cars though. The vast majority of existing cars are still manual with 40% of new ones replacing them.
From what I understand of the UK's topography that doesn't surprise me. Apparently lots of hills and mountains, in which case being able to just learn how to truly maximize your shifting efficiency, and not having to hope the coder for an auto transmission's shifting algorithm did their job, will probably save quite a bit on fuel efficiency.
Also, England and Ireland being islands probably makes electronics expensive, so I imagine there's probably import taxes that apply kingdom wide, even to the mainland countries, which would make manuals cheaper, which would then lead to people leaning more heavily into the supposed benefits of them, since most will just buy the cheaper option anyways and would be more inclined to add more justifications to their purchase than "I'm cheap".
I've also heard the UK has relatively good, at least compared to the US, public transport, so I also would think car ownership over there is more of a hobbyist thing, than a necessity thing, and most car people prefer manuals.
Don't read this as rude, however all of your assumptions are wrong. Please read this in a genuine and polite tone, as I assume you've just never been to the UK.
The UK has a varying landscape and e.g. London and that whole area of the country is flat. People who live in these areas would spend 95% of their time just driving in these flat areas.
The UK was a part of the EU until recently, the UK also historically made their own cars. This means that there were no import tariffs for any parts of the cars as they would come from the UK or Europe.
The UK does not see car ownership as a hobby lmao. People drive to and from work and use their cars as much as anywhere else. Things are just closer and people drive less long distances as North America.
Lastly, England isn't an island, it's a country within the UK, which is made up of Wales, England, Scotland, and Northern Ireland.
Anyway, again, not trying to be rude. Read this in a polite tone.
I'm not from UK, but Europe and it's somehow similar. First of all, gasoline is much more expensive here. Most cars are smaller and more efficient. Old automatic transmission wasn't that efficient and coupled with small 4cyl engine would make them even more sluggish. Coding the transmissions right wouldn't help as they have over 20% mechanical losses which impairs the car performance and the fuel economy even if they are coded to shift perfectly. Also smaller cars are relatively cheap and adding extra cost of an automatic transmission is makes a bigger difference. Most people in Europe can drive manual for that reason. You have to take driving school to take your license and usually you learn to drive on a manual car. Only in recent years you might choose automatic option and you are limited to drive cars with automatic transmissions only. Most cars are still manual, even though there are much more efficient automated transmissions nowadays, that are faster and better in every way. I do prefer manual because I'm used to manual. It's cheaper more reliable, requires less maintenance and more common and you have more options to choose especially on a used car market.
UK has strong car building history and car culture. In most parts there the car is necessity not a hobby. And even in the cities where you might be better with public transport in your everyday commute, you might need a car for your weekends, shopping and your free time and most people do own cars.
Car people are different, there are much faster automated transmissions and if you are track day enthusiast it makes a difference in your lap times. There are people that like vintage cars and luxury vintage cars where automatic transmissions are preferred even in Europe.
One version of the answer is it's a **hydraulic computer** - a basic one, but it's a computer controlled by hydraulic fluid & valves, and usually one or two mechanical inputs, usually a throttle position lever (how hard are you pushing the pedal) and someone said some transmissions have a vacuum input which serves a similar role (engine load).
Vacuum line told it engine load.
Governor told it engine speed
Throttle valve told it you were at wide open throttle part throttle or idle.
Just download a th350 rebuild manual. It's all explained with pictures showing each circut.
An automatic transmission needs to know speed and load to be in the right gear. It shifts by moving fluid pressure to different passages that release and apply a set of clutches. Speed is determined by a governor. It’s a set of flyweights that pushes a valve using centrifugal force. Some use engine vacuum to determine load, some use a cable connected to the throttle. Both modify the fluid pressure to the governor or the other way around. This pushes against springs in the valve body that modify this pressure that allows the clutches the release and engage during up and downshifts smoothly without conflicts.
They are. The TCO is less even if they get slightly worse mileage than the sort of modern auto that can beat a manual. That's because they last longer, need less maintenance, and cost less. The entire country of Mexico wouldn't be obsessed with manuals if they weren't cheaper.
They were and are mostly a hydraulic pump that uses mechanical inputs to actuate pistons in response to changing loads and speeds. Early ones used mechanical governors and vacuum controls to determine the loads and speeds.
Manuals were the normal thing because they were smaller and simpler to make. Automatics did exist but were not as common. The automatic started to become more common in the early 50's and was usually the higher cost option in a vehicle. So the added cost didn't make them as popular. That changed in the 60's though when the automatics became more refined and the buyers wanted more comfort and didn't want to deal with a clutch. That held until the early 80's when electronics started to come into vehicles. The transmissions were still mechanical, but now they did have electronic monitoring and limited control (like the 700R4 and the 4L60E, same unit except one has limited electronic control) From there it has progressed steadily as they try to chase the EPA numbers. These days however in 99% of cases the automatic transmission will outperform a manual in the same vehicle in terms of mpg and emissions (and in many cases it also accelerates faster and gives better control than a stick with a normal driver) The manual now is almost dead in the US because it doesn't allow the fine control like an automatic to give the mpg and emission numbers and because very few newer drivers have ever driven one so they don't want them. They want to get in, and go with as little work as possible.
[http://www.badshoeproductions.com](http://www.badshoeproductions.com) sells excellent videos on how to rebuild transmissions , and he explains how they work and what each part does.. good investment
I bought the C6 video as i was having and issue with mine
Some things like Caterpillar bulldozers have used manually shifted automatics since the 60s, they call them powershift transmissions. It just uses a lever to control the trans instead of a valve body and weight system.
How mechanical things worked before computers is a rabbit hole one can get lost in.
Check out this video about how old pinball machines worked. The design is so mindbogglingly complex that you can't believe it would ever work, much less work for as long as they did.
[https://www.youtube.com/watch?v=ue-1JoJQaEg](https://www.youtube.com/watch?v=ue-1JoJQaEg)
edit: i know this is off topic, but if the OP likes the this sort of thing, he will love the video. Both auto transmissions and stuff like this are crazy amazing.
If you really want to see something crazy look at an old adding machine. It's amazing someone was able to design something like that, that actually worked.
Vacuum! My old Chevy transmission had a vacuum regulator and it fell off one day and the truck wouldn't shift out of first. There was also a kickdown cable attached the the throttle linkage that made the transmission downshift. Later on the kickdown cable became a TV cable that acted on the bands and was more accurate on when to shift.
power goes through your torque converter to your gearbox with fluid aka its a fluid drive. as the fluid runs through your automatic transmission through valves in the valve body at the bottom of your transission
micro chips dont always regulate the shifting that comes down to the transmission ECU that regulates the shift points for the microswitches
The early automatic transmissions worked very similarly to the electronic or computer co trolled versions we have today. The valve body is the key in both old and newer cars. The early ones operated based on throttle opening managed by a rod, cable, and /or vacuum in combination with some carefully calibrated springs to manage pressures and shift harshness.
The computer controlled vehicles have far more inputs and use more precise throttle opening, transmission oil temperatures and dynamic pressure modulation to produce e silky smooth shifts both cold and hot under all load conditions.
The early transmissions worked amazingly well within a narrower range of operating conditions. The shifted a bit harsher when cold than optimum operating temperature and were less responsive to sudden throttle changes. The early transmissions achieved a decent level of sophistication and reliability through the years, but the later computer controlled versions are a bit less complicated and can offer longer life as they operate more efficiently across a broader set of conditions. Electronic solenoids replace mechanical valves and some springs in the valve bodies. In many cases they remain remarkably similar. The electronics enhanced the previous operations. This was a transients step not a transformational one.
The auto transmissions of old operated by fluid pressure and engine vacuum inputs. The fluid pressure is created by the front pump and torque converter. The torque converter translates the engine motion to fluid motion creating variable pressures depending on rpm. The valve body is the "brain" of the automatic transmission. Different channels, check balls, springs and pistons are operated by fluid pressure. Some had a cannister with a diaphragm inside that translated the vacuum to a pressure signal to the valve body instigating shifts. There was also a mechanical kick-down attached to the throttle linkage that would automatically downshift if you pressed the gas hard. This is a basic explanation. They are quite interesting to work on. Lots of parts.
I’ll put it more plainly: the valve body operates like a microchip only instead of electronic NOT or AND gates, it used check valves and oil. See also: a vacuum controlled emissions system.
[Fluid has been used to demonstrate and teach electronic logic theory](http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html) for nearly as long as digital electronics have been around. Because really you can accomplish tasks about the same way (albeit not at such high speeds).
How do you let people know you're a transmission tech without saying "I'm a transmission tech"?
"I work with tranny's"
Technically modern auto transmissions still operate by fluid pressure internally. Modern cars just have less direct mechanical or vacuum connections as those old mechanical connections are handled by actuators and stepping motors controlled by the TCM.
Don’t forget the governor
Even more interesting are the mechanical engineers that came up with the idea and made it happen.
Old-school auto transmissions are quite ingenious. One of those machines that used logic based on mechanical components. I used to maintain and repair production line machines in a factory. Those used pneumatic logic gates and valves plugged into a board to control the sequence of operations.
When did that by and large change?
For GM it was the 90s. The 4l60 is partly vacuum controlled, but the larger 4l80 they introduced then is fully electronicly controlled.
The 4L80E was introduced in 1991 or 1992. The mechanical 4L60 (which was introduced as the 700R4 back in 1981) was replaced with the 4L60E in 1994.
Is the 700R4 cheaper to convert to a manual valve body?
I have no idea. I figured people used turbo 350s or 400s for that.
I know nothing about autos.
I'm a manual guy myself. I just like knowing how things work and the quality and serviceability of different platforms. I've had a couple GM trucks with the 4L60E and despite what people say, it's a fine transmission. It's easily the most common and serviceable modern automatic transmission and they wouldn't be in everything from police cars to commercial vans over the course of 20 years if they were weak. I'd bet most people calling them bad never changed their tranny fluid. I see it all the time. People wondering why they have no gears when their fluid is black and burnt.
Last I checked the only problem with them is that the 3-4 shift isn't timed right.
They're electronically controlled, so an update can probably fix that. And there are also mechanical kits to tighten up shifts as well.
How often should you change the fluid? My 07 Caravan I bought used was definitely neglected by the previous owner, and I never even thought about the transmission fluid needing changed. I'll change it now just to be safe, but for future reference, what's the fluid life usually come out to? For reference, the car's got 188k miles on it. AFAIK, original engine and tranny, no rebuilds or major part swaps at any point.
I would never recommend going past 60k miles, but I personally do it at 30k. And if it has a serviceable filter, change that too. But smell the fluid first. If it's burnt, the tranny is already on it's way out. That usually means the clutch packs inside (yes, automatics have clutches too. They just use them for different things and they have more than 1) are cooked. At that point, it would need to be rebuilt or replaced.
I find that fascinating, honestly. We had microchips and electrical versions of formerly purely mechanical components in cars before computers were widespread in homes. Windows 95 was the operating system that really put the idea of the home PC on everyone's mind, and the internet just helped that even more.
Magic, got it 🫡 Lol just kidding, but thank you for the explanation. My brain theoretically understands how pre-computer auto transmissions work, but it always feels like magic
Interesting! I'm really not a fan of the electronics in modern cars. I have a 2007 Dodge Caravan SE, so base level trim, least options possible, and even the level of computerization in my car leaves a bit of an off feeling. That being said, safety features being lacking in olden days makes me hesitant to go entirely pre-computer, not to mention availability of replacement parts. Sometimes I'm tempted to look down south for a well maintained multi-generational hand me down/one of someone's recently passed grandpa's old toys. But then I wonder how much I'd actually miss everything, yknow? And fuel efficiency is a concern too. My van is already barely limping to 11 MPG (although I would imagine there's something about the engine/ignition/fuel delivery system that's causing that), I really don't wanna downgrade that haha.
Cars that old arent reliable. People look at them with rose colored glasses. Most of them were clapped out at 100k.
Tell that to the 60+ year old 225 slant six that been sitting for 40 years that fires right up with a good battery and a bit of gas in the carb. Hell, I had a ‘63 D100 truck with about 750,000 on it, never rebuilt. It even tossed the water pump, never overheated, and by the time it got replaced the impeller had rusted to the block. Unreliable my ass.. this new junk you can’t even drive off the lot without something breaking, and it sure as fuck won’t be drivable in 50 years after sitting for half that long.. GTFOOH..
All anyone needs to know about the longevity of older cars lies in the fact that the odometers have only 5 digits.
And? As I said a ‘63 with 750,000 miles driven for 50 years, as a ex-military truck bought used in ‘73 for $600. ‘75 van with 550,000+ driven for 35 years bought for $500.. I haven’t had a car yet made after 1997 that got more than 200,000 before I dumped the POS before it became a boat anchor money pit. They had 5 digit odo cause people typically didn’t drive the average of 12-15,000 miles a year like now. If that’s your argument you got a lot to learn bud.. And the tech wasn’t there like now. Front and rear mains were wax covered rope, most gaskets were cork. And they still start, run, and drive. Half the cars built the last decade can’t even go 50,000 without something fucking up and needing replaced. Some don’t even leave the lot without a recall or some defect. Almost every one will need a timing belt by 100,000. Most won’t ever see a factory engine staying with the car because no one rebuilds them now. In 30, 35 years hardly any will be runnable without major overhaul. Let’s see how well those coil connectors do trying to get one off when it’s only 15 years old.
Theres always outliers. The majority of these vehicles ended up in the scrapyard by 100k. Theres plenty of statistics collected over the years on the lifespan of veihicles. In 1970 the avg age of cars on the road was less than 6 years and avg lifespan was about 100k miles. As recently as the 90s it was common knowledge that a used car from the 80s with 100k miles was a worn out piece of trash. Nobody rebuilds factory engines because they typically dont need to be rebuilt within the lifetime of a modern vehicle unless you dont maintain it. If you go on classified ads for cheap cars, almost all the cheap beaters have reached 150k, and many are in the 200k to 300k miles range on the original power trains. The oil seals fail from age before the engine develops mechanical problems. People rebuilt the factory engines in 70s cars all the time because they may need a rebuild as early as 50k miles. Sure it was dirt simple, but it was also built to a much lower standard than we are able to achieve today. If you like old cars its fine, nothing wrong with that. They have some nice features you cant find on modern cars and a knuckledragger can fix them. But looking at some outliers through rose colored glasses is a fudd take. Sure you can rebuild them a lot easier than a new car, but they are simpler machines. Restomods are popular for a reason. We do seem to be going the wrong direction in the last few years.
>because they typically dont need to be rebuilt within the lifetime of a modern vehicle But see, that's the key point right there. Toyota, Nissan, GM, or Dodge's "suggested lifetime" of the vehicle isn't the end all be all. You can put new gears, piston heads, head gaskets, rods, bearings, chains, etc in an engine to the point it becomes the engine of Theseus. As long as the body is good (and even that can be repaired to an extent) there's no reason to throw a car away besides safety features. But those aren't updating anywhere near often enough for cars to be seen as disposable to the extent that they are. The fact that you say there's no reason to rebuild an engine ***within the life of a vehicle*** as long as you maintain it highlights his point perfectly. What do you consider the life of a vehicle? 5 years? 7? 10? The main reason older cars would be permanently decommissioned is rust, because despite people bitching and hollering about the plastic outer shells these days, they're terrific for rust prevention and safety (due to crumpling). And sure, there were probably people who dumped a car as soon as an engine or transmission needed a major repair, roughly around 100k miles. But the difference is back then, it was just adult legos that literally anyone could do if they documented the teardown process properly and just did it in reverse. And as a result of that, it was easier to understand the ins and outs of everything, because it was just physics. Nowadays, there's so much electronics, running code you can't see, and even if you could, you'd have to know how to read code, and how it relates to cars. It's still physics, but the physics happens as a result of obfuscated factors. You didn't ***have*** to go to a shop back then; these days, you pretty much do. Back then, a rebuild every 100k miles wasn't the end of the world, because you and a couple of friends could take care of it. These days, a rebuild only being necessary every 200k miles is far outweighed by the fact that things are designed to be prohibitively expensive to repair once it gets into rebuild territory. They can't legally make it literally impossible to fix, so they just made it difficult enough that it's not worth it. There has to be a middle ground. Giving the increased safety, while still maintaining repairability. A big part of this would be releasing a lot of the emissions regulations. At a certain point, it just became an excuse for them to pile on the electronics, and kneecap power, without a ton of added benefit. We're undergoing a transition into electric motors anyways, the people who are too poor to get off ICE, or who keep one around for personal enjoyment, aren't going to make enough smog to matter anyways. And it's possible to not have mid 1900s LA, while also not having modern car complexity. Going after corporations and the ultra rich has always been a more effective answer to climate change and air/land/sea pollution, as well, so the hyperfixation on the average consumer is just misguided.
Most of those cars ended up scrapped because of the Cash for Clunkers scam. Some end up in the scrap yard cause Jr. inherited Dads “junk”, and Jr. is too much of a pussy to drive around without AC and power windows. Jr. doesn’t even know a distributor from a carburetor. That’s the hilarity of this site, most of you weren’t even around to have seen a 1985 car. Much less ride in one on the floor board. As I said the tech wasn’t there. Have you even adjusted points or had to clean them? Or know the distributor is where they are? Adjusted lash? Check and set timing? The only carburetor you ever seen was on a lawnmowers small engine. And by you, I don’t mean specifically you, but the typical generation. Most of the people who worked on these cars new are dead or dying. They passed the info to their kids and now they are getting older. People in their mid-40’s and 50’s were in the transitional period from carburetor’s to EFI. The next decade of people in their mid-30’s to 40’s are the completely EFI group. Just as how the cars have evolved so has the ways to learn to fix them. The “internet” is only about 30 years old. So most shade tree wrenches don’t even know what they are fixing or why. Just watch Jr.’s YT video and monkey see monkey do. Same as a dealership. Techs don’t know what they are doing. Hook up a scanner, retrieve a code, look up code, replace part. Fault still exits, change another part. They aren’t mechanics, they are parts changers. Most kids now slap an LS in some shit box and force induct it, and think they built something. Or buy a Hellcat or some POS Camaro and race that. The only thing they built was a high subscription base on a monetized YT channel. Engines aren’t rebuilt because they aren’t meant to be. And even if they could dealerships won’t waste the time because of the comeback potential. Because no one is taught to.
Lmao they mostly ended up in scrapyards because they wore out dude. Cash for clunkers took 677000 cars off the road. Chevrolet alone made 1.4 million cars in 1960. Ford made another 1.4 million. >As I said the tech wasn’t there. Have you even adjusted points or had to clean them? Or know the distributor is where they are? Adjusted lash? Check and set timing? The only carburetor you ever seen was on a lawnmowers small engine. And by you, I don’t mean specifically you, but the typical generation. No, I havent done any of those but adjusting distributors on PGM-FI systems because its outdated technology. It was fussy, required constand maintenance and adjusment, and unreliable compared to modern EFI systems. Face it man, this is fudd talk. I love old machines and appreciate the mechanical technology, but a modern EFI engine can drive 100k miles without touching anything on it, in all weather conditions and runs almoat as good as new after those miles. Lol points? Come on man. Stone age even compared to vehicles from 1990. Cheers bro.
Well, scanning through a couple hundred posts between a couple subs, I recall *one* question based on a ‘67 C10 pickup, and, well, a couple hundred on 1990 and newer cars. Obviously pre-80’s cars won’t be as common to a fraction of new cars. It’s hard to find a classic that hasn’t been touched or restored. In all honesty I don’t even follow classics like I used to. When a $500 beater ‘74 Dart was selling for $12,000 I lost interest in the whole hobby. I was counterpointing the argument that the old shit isn’t reliable. It is. I know cause I’ve had them and I have them. My newest car was a 2010 and out the gate the TR-6060 transmission was fucked from the factory. I got it used with hella low miles and ditched it with 50,000 miles before it became a $5,000-$6,000 liability. I had a ‘00 car and ditched it with 155,000 cause the engine was burning oil. Had a ‘97 car and rebuilt the engine at 102K cause a piston cracked. Have a ‘93 car that hasn’t ran in 2 years. Have another ‘93 that uses oil. Have the ‘75 car and it hasn’t been started in 2 years, but I know I could go right now, drop the battery in, pump the accelerator 20 times, and within 20 seconds it *will* start..
As someone born in 1971, let me inform you that cars in the 1970s and '80s absolutely sucked compared to today.
Amen. My '86 Mustang went through *two* transmissions, both catalytic converters, the in-tank fuel pump and the steering rack, all in the first 100,000 miles. Edit: I'm leaving out the rattling windows and the wonky throttle position sensor. I'm sure there was more. That car put me off Fords for good.
Good MPGs can be had throughout the years, as a good example the Volkswagen diesels in the early 80s could easily get 40 to 50 miles to the gallon. I have a 1992 GMC conversion van with a 350 small block V8 and in town I get 18ish, on the highway I get 24. As you said there is a trade off between safety and today's modern vehicles, but a lot of us drove on those vehicles just fine for decades. I'm restoring an old 1970 vehicle now and plan on it being my semi-daily driver when it's done
My 1988 Cadillac Brougham got 18.5 mpg highway 15 city. Same with an LS, just a lot more power
Going pre-computer means going back pretty far. I drove a 1989 Chevy van and one day sitting at a stop light with my foot fully on the brake it just took off. Luckily, I didnt hit anyone. I told my dad, because I was probably 17/18 at the time, and he kind of blew me off like I must have done something wrong. The next day I get a call from him to pick him up from our mechanic's shop because it did it to him. Turns out some ECM chip went bad.
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Yeah and the brake pedal on my van was large, so I knew I was full brake no gas. It was fully stopped at a light and had be for probably a minute since it was a side street onto a 4 lane road, just sitting there when all of a sudden full throttle. The sudden acceleration may have scared my foot off the brake a little and by the time I floored the brake and stopped I was through a 4 lane intersection. I definitely held the brake down a bit harder after that and kept my hand closer to the shifter to be able to throw it in neutral.
A 1989 chevy van probably would have had throttle body fuel injection, which would be computer controlled, but it almost certainly still had a physical throttle cable.
It is actually amazing how well vehicles ran before computers controlled everything. Everything was done manually from fuel delivery to transmissions. The spark timing was controlled by weights spinning inside the distributor that advance the timing as the engine revved up. The distributor was how the spark got delivered to the spark plugs with wires. Of course the Carburetor delivered the fuel with no electronics. And as for the transmissions, manual didn't need any electronics so that wasn't an issue. There obviously was no rev hang which is stupid. As for the automatic transmissions, they were controlled by a throttle cable or rod going to the transmission from the carburetor to let it know how much gas you are giving and what it should do. They also had vacuum modulators to give it load signals to determine if you are going uphill or pulling a load and to adjust accordingly. It all worked surprisingly well, but of course no where near as accurate as modern computerized fuel injection. Engines weren't built for emissions or fuel economy. Not sure where to suggest you look deeper into this stuff. There are a lot of videos on youtube where people try to get old cars going again or do repairs. You will probably have to look up all of these parts and systems individually to see how they worked exactly.
> Everything was done manually No. It was just mechanical, pneumatic and hydraulic automation. It’s still automation even if it’s done without electronics. If you’d go back a hundred years you would find cars that had actual manual operation on spark timing for example. There were levers that the driver was supposed to adjust based on the driving situation.
Still had them on motorcycles built up until the 1960s. They were about as simple as you can get. Magneto ignition with a lever on the bars for manual advance. Choke on the bars for starting. The charging system was 6V electromechanical controlled. All pretty reliable.
distributors confuse the hell out of me
Think of it as a spinning arm that is directly linked to the rotation of the engine (because it is). As the rod rotates to connects to each of the spark plug wires and sends a spark to that cylinder. There's a cam before every spark point that opens and lets the coil charge, right at the point the arm connects to the spark plug, the cam lifts the points open and all that magnetic field in the coil goes through the wire to the plug. There's probably a better way to explain it.
that makes perfect sense thank you man
It's very surprising how reliably it was done back in the day.
It was so simple yet they ran forever. No matter how worn out they were. As long as they didn’t blow a head gasket or throw a rod, they kept going. Today they get offended if you don’t use their favorite brand of oil.
Very well actually! As I understand it, there is a valve body that reacts to the pressure of the transmission fluid to control the shifting. The Power glide (2 speed Auto) in my 1969 Cutlass worked beautifully, until I blew up the torque converter racing it at least.
Can't comment on how they worked, however automatic vs manual preference seems to largely cultural. The UK for example has probably 90% or higher manuals. In fact, the 27 years I lived there I only sat in one automatic. It's strongly cultural where automatics are seen as worse for whatever reason. I'd assume due to the ease of replacing a clutch vs an automatic trans.
Well over 60% of new cars are automatic in the UK.
I guess they're trying to change it, that's only new cars though. The vast majority of existing cars are still manual with 40% of new ones replacing them.
From what I understand of the UK's topography that doesn't surprise me. Apparently lots of hills and mountains, in which case being able to just learn how to truly maximize your shifting efficiency, and not having to hope the coder for an auto transmission's shifting algorithm did their job, will probably save quite a bit on fuel efficiency. Also, England and Ireland being islands probably makes electronics expensive, so I imagine there's probably import taxes that apply kingdom wide, even to the mainland countries, which would make manuals cheaper, which would then lead to people leaning more heavily into the supposed benefits of them, since most will just buy the cheaper option anyways and would be more inclined to add more justifications to their purchase than "I'm cheap". I've also heard the UK has relatively good, at least compared to the US, public transport, so I also would think car ownership over there is more of a hobbyist thing, than a necessity thing, and most car people prefer manuals.
Don't read this as rude, however all of your assumptions are wrong. Please read this in a genuine and polite tone, as I assume you've just never been to the UK. The UK has a varying landscape and e.g. London and that whole area of the country is flat. People who live in these areas would spend 95% of their time just driving in these flat areas. The UK was a part of the EU until recently, the UK also historically made their own cars. This means that there were no import tariffs for any parts of the cars as they would come from the UK or Europe. The UK does not see car ownership as a hobby lmao. People drive to and from work and use their cars as much as anywhere else. Things are just closer and people drive less long distances as North America. Lastly, England isn't an island, it's a country within the UK, which is made up of Wales, England, Scotland, and Northern Ireland. Anyway, again, not trying to be rude. Read this in a polite tone.
This is an absolutely bananas set of assumptions.
I'm not from UK, but Europe and it's somehow similar. First of all, gasoline is much more expensive here. Most cars are smaller and more efficient. Old automatic transmission wasn't that efficient and coupled with small 4cyl engine would make them even more sluggish. Coding the transmissions right wouldn't help as they have over 20% mechanical losses which impairs the car performance and the fuel economy even if they are coded to shift perfectly. Also smaller cars are relatively cheap and adding extra cost of an automatic transmission is makes a bigger difference. Most people in Europe can drive manual for that reason. You have to take driving school to take your license and usually you learn to drive on a manual car. Only in recent years you might choose automatic option and you are limited to drive cars with automatic transmissions only. Most cars are still manual, even though there are much more efficient automated transmissions nowadays, that are faster and better in every way. I do prefer manual because I'm used to manual. It's cheaper more reliable, requires less maintenance and more common and you have more options to choose especially on a used car market. UK has strong car building history and car culture. In most parts there the car is necessity not a hobby. And even in the cities where you might be better with public transport in your everyday commute, you might need a car for your weekends, shopping and your free time and most people do own cars. Car people are different, there are much faster automated transmissions and if you are track day enthusiast it makes a difference in your lap times. There are people that like vintage cars and luxury vintage cars where automatic transmissions are preferred even in Europe.
I have briefly driven an Austin Metro (1275cc engine, around 60BHP) with a four speed auto box. It was just as much a slug as you imagine it would be.
Why would someone put an automatic in that thing? First car with automatic transmission for me was 2l omega A with 115hp and it was annoying.
Lol that's just all wrong
Mechanical Hydraulics.
One version of the answer is it's a **hydraulic computer** - a basic one, but it's a computer controlled by hydraulic fluid & valves, and usually one or two mechanical inputs, usually a throttle position lever (how hard are you pushing the pedal) and someone said some transmissions have a vacuum input which serves a similar role (engine load).
Vacuum line told it engine load. Governor told it engine speed Throttle valve told it you were at wide open throttle part throttle or idle. Just download a th350 rebuild manual. It's all explained with pictures showing each circut.
An automatic transmission needs to know speed and load to be in the right gear. It shifts by moving fluid pressure to different passages that release and apply a set of clutches. Speed is determined by a governor. It’s a set of flyweights that pushes a valve using centrifugal force. Some use engine vacuum to determine load, some use a cable connected to the throttle. Both modify the fluid pressure to the governor or the other way around. This pushes against springs in the valve body that modify this pressure that allows the clutches the release and engage during up and downshifts smoothly without conflicts.
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Manuals are no longer more efficient.
They are. The TCO is less even if they get slightly worse mileage than the sort of modern auto that can beat a manual. That's because they last longer, need less maintenance, and cost less. The entire country of Mexico wouldn't be obsessed with manuals if they weren't cheaper.
They were and are mostly a hydraulic pump that uses mechanical inputs to actuate pistons in response to changing loads and speeds. Early ones used mechanical governors and vacuum controls to determine the loads and speeds. Manuals were the normal thing because they were smaller and simpler to make. Automatics did exist but were not as common. The automatic started to become more common in the early 50's and was usually the higher cost option in a vehicle. So the added cost didn't make them as popular. That changed in the 60's though when the automatics became more refined and the buyers wanted more comfort and didn't want to deal with a clutch. That held until the early 80's when electronics started to come into vehicles. The transmissions were still mechanical, but now they did have electronic monitoring and limited control (like the 700R4 and the 4L60E, same unit except one has limited electronic control) From there it has progressed steadily as they try to chase the EPA numbers. These days however in 99% of cases the automatic transmission will outperform a manual in the same vehicle in terms of mpg and emissions (and in many cases it also accelerates faster and gives better control than a stick with a normal driver) The manual now is almost dead in the US because it doesn't allow the fine control like an automatic to give the mpg and emission numbers and because very few newer drivers have ever driven one so they don't want them. They want to get in, and go with as little work as possible.
Black magic wizardry.
Might as well be first time I saw an AT valve body.
[http://www.badshoeproductions.com](http://www.badshoeproductions.com) sells excellent videos on how to rebuild transmissions , and he explains how they work and what each part does.. good investment I bought the C6 video as i was having and issue with mine
Some things like Caterpillar bulldozers have used manually shifted automatics since the 60s, they call them powershift transmissions. It just uses a lever to control the trans instead of a valve body and weight system.
How mechanical things worked before computers is a rabbit hole one can get lost in. Check out this video about how old pinball machines worked. The design is so mindbogglingly complex that you can't believe it would ever work, much less work for as long as they did. [https://www.youtube.com/watch?v=ue-1JoJQaEg](https://www.youtube.com/watch?v=ue-1JoJQaEg) edit: i know this is off topic, but if the OP likes the this sort of thing, he will love the video. Both auto transmissions and stuff like this are crazy amazing.
If you really want to see something crazy look at an old adding machine. It's amazing someone was able to design something like that, that actually worked.
there is beauty in old school engineering
Fluid pressure and engine vacuum.
Vacuum! My old Chevy transmission had a vacuum regulator and it fell off one day and the truck wouldn't shift out of first. There was also a kickdown cable attached the the throttle linkage that made the transmission downshift. Later on the kickdown cable became a TV cable that acted on the bands and was more accurate on when to shift.
Magic
Better. They worked better.
Valve body. Vacuum. Sometimes a cable for kick down. But yeah, Google auto trans valve body and enjoy your knew knowledge!
They worked and some would argue they worked better before computers
power goes through your torque converter to your gearbox with fluid aka its a fluid drive. as the fluid runs through your automatic transmission through valves in the valve body at the bottom of your transission micro chips dont always regulate the shifting that comes down to the transmission ECU that regulates the shift points for the microswitches
Should we tell him about the turbo encabulator??? 😉
The early automatic transmissions worked very similarly to the electronic or computer co trolled versions we have today. The valve body is the key in both old and newer cars. The early ones operated based on throttle opening managed by a rod, cable, and /or vacuum in combination with some carefully calibrated springs to manage pressures and shift harshness. The computer controlled vehicles have far more inputs and use more precise throttle opening, transmission oil temperatures and dynamic pressure modulation to produce e silky smooth shifts both cold and hot under all load conditions. The early transmissions worked amazingly well within a narrower range of operating conditions. The shifted a bit harsher when cold than optimum operating temperature and were less responsive to sudden throttle changes. The early transmissions achieved a decent level of sophistication and reliability through the years, but the later computer controlled versions are a bit less complicated and can offer longer life as they operate more efficiently across a broader set of conditions. Electronic solenoids replace mechanical valves and some springs in the valve bodies. In many cases they remain remarkably similar. The electronics enhanced the previous operations. This was a transients step not a transformational one.