Got to thinking: Auto Trans Coolers

[Bob_Sheaves]

OK, give me a couple of days to assemble all the reference material I will need then I will start the new thread.

Best as always,

Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions.com

 

[ntsqd]

Re: Aux Cooler in parallel with the radiator cooler, I personally would only do this with the t-stat mentioned above. They can be had from several sources, but here's an easy link: BAT-Mocal Then the aux cooler is bypassed until needed, allowing the stock cooler to - in the case of cold weather - keep the trans up to a reasonable temp while still providing hot weather/high stress cooling.
There is no reason that this couldn't be used with a series plumbing arrangement, to the same end.

As I initially pointed out, the downside to running an aux cooler after the stock cooler is that this has the potential to elevate the temp of the 'cold' water supply to the engine during high cooling stress situations. I won't say this is a bad arrangement, but it wouldn't be my personal first choice.

Something that should probably be stated for those who haven't had any sort of thermaldynamics education. That is that the more radical the temp difference, the more radical the reaction. In other words the bigger the difference in temp between the two fluids (air being a fluid) the better a heat exchanger (cooler or radiator) will work. This is intuitive, it's what you'd expect if you've given it any thinking, but it's not necessarily all that obvious. Back in the days of my A/C-Refridgeration class my instructor demonstrated this with an experiment that would likely result in some kind of citation today. He poured room temp water into a styrofoam cup, and then poured liquid CFC refridgerent (R12) into the cup. It made a cool looking ice sculpture. Then he did the same thing with boiling hot water. It blew the cup apart!

Thanks, Bob. I'll keep an eye out for it.

 

[CJinCA]

An aspect overlooked with the cooler in series after the radiator is that the total system temp for the ATF is lowered, reducing the ATF temp that enters the radiator as well. If one is worried about the heat dump to the radiator from the ATF causing the engine to overheat, the cooling system is marginal at best. Better off in the long run to upgrade the cooling system and not concern oneself with the relatively small cooling circuit for the ATF in the radiator.

Here's a little tip if you are overheating - turn on the heater inside the cab. That will lower the engine coolant temp as the term heater core is just another word for radiator.

There's no need to bypass the auxiliary cooler "until needed" with a thermostat. As I mentioned, it's an extremely rare occurrence to overcool a transmission. But the heat problem is almost always there. Even in the far north in the dead of winter, ATF can get overheated for a variety of reasons (rocking, heavy loads, wheel spin, etc.).

When in doubt about such things, the logical and expedient thing to do is seek out and check and verify with service personnel in the field who have actual "nuts 'n bolts" experience. By checking with repair facilities in the far north and also national trade organizations, one can learn what works and what does not. Much simpler but admittedly not as much fun if one enjoys playing with gadgetry and attempts at reinventing the wheel. Food for thought.

If you have any more questions, post ‘em up and I'll try to help you out. Good luck!

 

[Erick Lihme]

I'll just throw in my .02 cents.



Living in the "far north", on a 85' Toyota 2wd which is used for towing, a 3 core radiator was added with a large trans cooler run in seris ahead of the stock radiator cooler. The trans heats to operational temps in sub zero temps just fine. After 25,000 miles, the ATF is as pink as the day it was installed. The fan clutch almost never engages.

This is was done on the advice of a retiring master trans mechanic. It should have a very long service life as result. As a measure of this set up, the original 52,000 mile fluid was dark, driven unloaded with mostly city miles.

 

[ntsqd]

snippage.....
An aspect overlooked with the cooler in series after the radiator is that the total system temp for the ATF is lowered, reducing the ATF temp that enters the radiator as well.

Not necessarily. There is a significant heat adder not accounted for, the prime heat generator in an auto trans, the torque converter. If we assume that the delta T across the T/C remains constant regardless of intake fluid temp, then maybe. If there is some other factor limiting or affecting actual trans fluid outlet temp then I don't know. I'm waiting to see how the math works out b4 much more comment.

 

[CJinCA]

Not necessarily. There is a significant heat adder not accounted for, the prime heat generator in an auto trans, the torque converter. If we assume that the delta T across the T/C remains constant regardless of intake fluid temp, then maybe. If there is some other factor limiting or affecting actual trans fluid outlet temp then I don't know. I'm waiting to see how the math works out b4 much more comment.

Not quite sure why one would not account for the torque converter when figuring efficiencies of auxiliary coolers, unless one was running a Clutch-Flite, Turbo-Clutch or something similar. But that stuff is old school tech for the drag strip and most of those guys didn't run any coolers at all, short of a deep sump pan. Hardly the kind of stuff one will find out on the trail.

Yes, the torque converter is THE heat generator in an auto trans. In a properly functioning and shift-timed transmission, the trans proper generates very little heat. If the torque converter is taken out of the equation, I wouldn't have many qualms about running without a cooler entirely. Not much different than a manual trans really when concerning heat produced without the torque converter in a correctly calibrated auto trans. What that means is good shift quality for the application with minimal slippage.
.
Externally, another aspect overlooked is the exhaust system. Depending on circumstances, the engine exhaust system can be the equal of, or in some cases exceed torque converter heat influenced on the trans. Inadequate clearance of cats and running cooler lines close to headers and pipes can really elevate trans temps.

Ford always comes to mind as the worst-case scenario for poorly planned factory exhaust systems. Late ‘70s to early ‘80s Ford intermediates were running dual cats, one on each side of, and in very close proximity to the trans. That design sent tens of thousands, if not hundreds of thousands of C4s and FMXs to a very early grave. Failures due to heat in as little as 40,000 were quite common. Those cats cooked the ATF, turning it to varnish.

With automatic transmissions, it's always a good idea to consider exhaust heat when designing or modifying an exhaust system or installing or rerouting cooler lines. Good planning, keeping the exhaust heat influence on ATF to the practical minimum, can greatly reduce the burden on the cooling system.

I'll just throw in my .02 cents.

Living in the "far north", on a 85' Toyota 2wd which is used for towing, a 3 core radiator was added with a large trans cooler run in seris ahead of the stock radiator cooler. The trans heats to operational temps in sub zero temps just fine. After 25,000 miles, the ATF is as pink as the day it was installed. The fan clutch almost never engages.

This is was done on the advice of a retiring master trans mechanic. It should have a very long service life as result. As a measure of this set up, the original 52,000 mile fluid was dark, driven unloaded with mostly city miles.

Great cooling system upgrade Erick. As you say, it should live a long time.

One of the things that I dislike about many of the new vehicles today is the lack of a trans dipstick. You have to crawl under the vehicle and pull a plug to check the level and condiiton. It's always comforting with the older vehicles to be able to quickly pull the dipstick and survey the condition of the ATF as you do.

Thanks for the feedback on the cold country.

 

[Erick Lihme]

"One of the things that I dislike about many of the new vehicles today is the lack of a trans dipstick."

Are the newer Toyota's without a dipstick? In general, the old and slow tech have many virtues lost on the next generation. If less fuel efficient verses horsepower, cost per mile is reduced with the easy of maintenance compared with the newer tech. Then factor in the total cost of ownership. Retired early, finances forces me to be practical, and wiser. I can pay cash for a brand new one, but why?

The 85' Toy is a substitute. If fuel where not such an issue, I'd still be driving the 72' 1/2 ton 4 WD Chevy. The 350 with a Turbo 350, and especially the Turbo 400, is a tough and durable combination.

Another thought and more rambling. History repreats, so wars and depressions will occur in the future. Should any of these occur in my life time, the next 20 years, with spare parts plentiful, and a knowlegable owner, the low and old tech 85' will survive like the cochroach that it is.

 

[CJinCA]

From what I've read, the new '05+ Tacomas don't use a dipstick. I'd imagine there's at least a few other Toyota models without a dipstick also. We have a 1998 Oldsmobile for a daily driver and it is sans dipstick as well. Gotta jack the thing up in the air or put it on a lift and unscrew a plug to check the ATF. A real pain in the ********.

Some folks say "So what. That's how you check the fluid in a standard transmission.What's so special about an automatic?" What they forget is that unlike standards, automatics have a half dozen or more places on them that are under pressure and sealed externally. Just a pin hole leak will spew out a good deal of fluid when pressurized. Not the case with standards.

So you see a few drops of what might be ATF on the garage floor at home. Could it be the trans leaking? Wanna check the level? But there's no !@#%&! dipstick. Start jacking the damn thing up in the air or take it to a shop, put it on the rack and have them check the level. GEEZ!!!

I could be wrong, but I think it was BMW that first used a "no dipstick" ZF transmission back in the early '90s. Toyota & GM have jumped on the bandwagon as well. I'd bet that Ford and Chrysler and some other imports are doing the same thing on at least some of there models. If I was purchasing a new vehicle today, and if it were an option (fat chance!), I'd gladly pay extra to have a trans with a dipstick and a drain plug in the pan.

I like the older stuff like you do. My last full-size was a short box 1/2 ton '79 GMC pickup. 400 small block, THM 350 and NP203 were a piece of cake to work on. But the mileage really sucked after a minor lift and installing 8 lug 3/4 ton differentials front & rear with 4.10 gears. I was contemplating converting to a 700R4 trans to help with the MPGs, but the truck got totalled before I got around to building a 700.

Ended up with a '00 Tacoma 4x that ain't too bad on gas. But like you say, gas mileage is secondary to reliability and you can hardly go wrong with a Toy for reliability.

Like you, I plan to drive the wheels off this one before replacing it. No sense in spending money when one makes due with you have.

And I love "the low and old tech 85' will survive like the cochroach that it is." That's classic!!!!!

 

[Erick Lihme]

Appreciate the comment. It does kinda of stick donut.

Regardless of fuel consumption, the early Chevys are still around in numbers because they are easy and cheap to maintain workhorses. I still have 62', my brother 2 flatbeds, 72'and 74', as well as a 2002 and 2003 Ford diesel 4WD's. The Chevy's will still be around long after the Fords (fancy junk BTW) are gone.
The Chevy's also offer the ability to carry loads.The old Toyota's would survive like the Chevy's if it were not for emmissions testing. They are the next best thing to an old Chevy.