They are advancing far far faster. The technology is changing daily. Most of the technology is in the software. Much easier to make changes to.
I agree but there’s another factor- gearing. Many years ago I was into drag racing and went against the grain so to speak. People wondered why I was so fixated on developing this funky transmission. The reason was gearing; the great equalizer. In the end, amoung other benefits, I had a transmission that could launch the car using a stock torque converter. And the trans temps were almost “normal” to boot.
A car that’s sitting at a stop light or doesn’t get to lock up speed is still generating copious amounts of heat by slippage of the converter. But with lots of gears, the slippage at speeds under lockup is reduced and certainly helps the thermal management issue…
I used to drive a 1950 Dodge sedan with three speeds and a fluid drive.
Simply put, fiction.
Did you mean friction, or are you trying to start a fight?
;-]
Unless your engine has a racing idle, I doubt that there is enough energy being delivered to the transmission to overheat it while sitting at a stoplight in drive. The surface area of the transmission case and oil pan can likely dissipate that amount of heat.
I believe that the oil coolers were added later to deal with worse case scenarios, just like radiator fans. Ninety percent of your driving could be done without a fan behind the radiator, same with transmission oil coolers.
Climbing long steep grades, towing heavy trailers, etc. is where the oil cooler is needed.
We’ll have to disagree on that one. The output shaft of the engine is turning at 8-900 rpm and the input shaft of the transmission is not. All of that energy is being dissipated by the hydraulic fluid in the torque converter. The fact it is partially dissipated by the fluid volume, contact surfaces and “cooler” doesn’t diminish the amount of heat being generated and localized temp increase due to the slippage.
The cooler is really a temperature regulator. It cools the fluid when it’s above the radiator coolant temp and heats the fluid when it’s below the radiator fluid temp. If it’s only job was to dissipate heat, it would be located outside of the radiator. They’ve been used a long time so the benefits were recognized back then.
But how much torque is the engine delivering to the transmission? 900 rpm times zero torque is zero power. How much rpm drop in an idling engine is there when you shift from neutral to drive?
The torque input is proportional to the square of the slip speed and at idle speed, there’s not really very much torque. It’s like an airplane propeller. At 600 rpm, the plane won’t even taxi and the engine is barely loaded, at 2700 rpm it takes all of the engine’s power and can take off and go into a steep climb.
Or to put it another way, with the engine idling at 600 rpm, you can stop the car from rolling forward by putting a two by four in front of the car’s wheels. At full throttle, the car smokes the tires.
There’s a lot more to the situation
http://www.google.com/patents/US4180977
than appears from the outside
Why are automatic transmissions cooled?
Coolers? I don’t think mine get much of a work-out. 
For a good portion of the year where I live I could use some automatic transmission heaters, like the units sold here…
Transmission Fluid Heaters | page 1 - Auto Cooling Solutions
CSA
There are a lot of good points in this discussion, particularly about how more heat is generated in automatic transmissions, particularly in the days of yore. I feel that one important point may be missing. Automatic transmissions are cooled, perhaps, because the fluid needs to be cooler than manual transmission “fluid”. It is different fluid, right? Assuming that crankcase oil and gear oil have similar thermal tolerances, or even that gear oil is intermediate in tolerance between ATF and crankcase oil, the ATF has lower tolerance for temperature rise. Some manual transmissions use regular crankcase oil don’t they?
Crankcase oil temperatures are supposed to be well above the boiling point of water for a significant proportion of the running time to purge water from the combustion blow-by. IIRC, the desirable range is something like 230-260 F. Trans fluid temps are limited to 195ish if possible. ATF does not have to get hot to purge moisture because there is no source of moisture. Since they can run cooler, I assume that some aspect of auto transmissions mechanical design and material choice (maybe the friction material or the fluid itself) can have superior characteristics if design limits include lower temp so it is designed for that temp and then MUST then be kept at that temp.
If anyone wants to poke a hole in this argument, welcome. One think that I don’ t know is what is a typical operating temp for a manual transmission, or a differential for that matter. If it gets up into the same range and higher than an automatic, then my argument is stronger.
1 Like
It has been my observation that engine oil in the pan usually remains below 190*F in daily driver automobiles.
Why are auto trans cooled? The people who designed it thinks it is a function for reliability and proper operation. That is all I need to know.
1 Like
None. 100% of the energy is being converted to heat energy in the torque converter and dissipated by the unit’s surface area as radiant heat and brought by the fluid to the tranny cooler to be dissipated into the outside air. A very small amount propagates to stuff that the tranny is bolted to, but that amount would be miniscule. The key parts of the tranny temperature management are the fluid and the torque converter design.
The amount of energy being generated in the torque converter at a stoplight in a fully warmed-up modern system is small. Modern cars will roll backwards in a slight incline if the brake is released. Tranny designers have become really good at designing in an almost total disconnect at idle in pursuit of the fed’s goal of extreme gas mileage.
The engine and transmission sharing oil is a very common practice in motorcycle engines and I believe the Ford Model T also used engine oil to lube the transmission.
Honda made a automatic version of the CB750 motorcycle in 1976, the CB750A, or Hondamatic as many called it. It had a two speed transmission and a torque converter. It wasn’t totally automatic, the rider shifted from low to high with a normal gear shift lever, but instead of moving gears on a shaft, it valved oil pressure to two different clutch packs, one or the other was engaged depending on which gear the rider wanted to use.
This transmission also shared the engine’s lube oil.
The thing that’s “special” about ATF is that it has to be compatible with wet oil bath clutch packs. The torque converter could care less if it was filled with ATF, engine oil, or hydraulic oil.
There are also some manual transmissions that specify ATF for the lube.
I’m not sure that’s accurate. Fluids of different viscosities will react differently in a fluid coupling device.
The coupling in a fluid coupling has more to do with the oil’s inertia than it’s viscosity. The pump accelerates the fluid and the turbine decelerates it. That’s how the torque is transferred from the pump to the turbine.
ATF is approximately a 5W-20 oil and is often used as a hydraulic oil, especially in car power steering.
The pump portion simply transfers energy through the fluid to the turbine. Viscosity, the resistance of the fluid to flow, definitely has an impact on the energy transfer. Different viscosity fluids will transfer energy differently. It’s important to have the correct fluid in an automotive transmission system. Incorrect fluid can cause too much of the energy to be converted into heat and too little converted into torque on the tranny’s input shaft.
If a system is designed to use 5W-20, than that’s the correct fluid. Engine oil can be used as a hydraulic fluid as well as a lubricant, and in fact is used in that manner in variable valve systems. It’s actually used as a hydraulic fluid in hydraulic lifters too. If you think about the manner in which it keeps the crank and rod bearings from premature wear, a pressurized fluid barrier, it could be argued that it’s used as a hydraulic fluid there too… although I’d be reluctant to describe its function that way except in a purely esoteric discussion. 
I once road a ferry over the Mississippi River and I was driving the only car making the ride but there were dozens of motorcycles carrying couples my age and older. All the bikes were 3 wheelers, most Honda trikes. It seemed that all were automatic transmission. It was difficult to not laugh at the not so easy riders who had gotten themselves in a knotted mess with their wives sitting behind them. Some had reverse but most didn’t and several had trailers. I’m glad I dropped the kick stand for the last time when I was in my 50s when I thought I could still look cool. A three wheeler with an automatic transmission and electric starter just isn’t a motorcycle.
1 Like
Oh, that’s debatable. The population is aging. There are a lot of us who love the ride, but can no longer kick over an engine or hold up a bike at a stopsign on an incline. Personally, I haven’t tried to ride a two-wheeler in many years, but I seriously doubt if I could now. I can barely walk… and than only for a short distance. If I did now get something, I’d be limited to something I could put my leg through… I could no longer swing my leg over the average fuselage.