How long can you run a trans without any cooler?

I know some people who race with just a loop and a finned trans pan.
They get a bit freaked though on a hot day when they are going rounds....undeneath car spraying trans pan.

 

As long as your not working the convertor (slipping/stalling it) your fine.

 

Apparently the temp levels get very high very quickly if you run a trans brake and sit on it too long. I understand ten - twelve seconds is enough to trash the clutches and steels.

 

Any amount of stall testing the converter against a transbrake is not recommended.. And that by the way is what gets beat up, the clutch packs are hydraulically locked up, so there is little concern for those parts, assuming the trans was built properly, and running the correct line pressure.

The pressures in the converter on the other hand get very high, very quick, and you want to keep you time 'on the brake' t0 a minimum.
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As far as trans fluid temp, there are two aspects to consider:

Efficiency - For low residual power loss, and the highest mileage available, you want hot fluid- 190+

Trans Lifespan- Heat is the enemy of the rubber and paper/cork seals and gaskets in your trans, from the piston lip seals to the pan gasket. The cooler the fluid runs, the better you are, and the longer the trans will last. In ambient temps above 40*F, it's impossible to "overcool" a transmission.

160-175 has often been considered as the optimum balance temp between the two.

The radiator "cooler" is misnomer... it is in fact a heat ex changer, and the only way it does any cooling is if the engine coolant is at a lower temp than the trans fluid, and this is rarely the case. Towing a trailer in the mountains and really leaning on the throttle, might get you there.

Race cars, and any type of warm weather only cruiser, by pass the radiator all together. Your not out for gas mileage here, so there is no reason to use it at all. Anyone that tells you different, just likes to argue.. you won't find a trans professional that will disagree with me, especially on the older non electronic transmissions.

The 05 3/4 ton Burby I just picked up, will have the lines from it's 4L80E divorced from the radiator cooler, and I will add another larger fin/plate cooler to supplement the small factory one. Had it been done this way in the first place, I might not have to rebuild it now.. since it's been smoked from overheating.. the fluid looked like used motor oil when I changed it. That vehicle is not going to be driven in cold temps. Divorcing the cooler circuit from the Radiator and adding another cooler, will result in trans temps in the 140-150 range, depending on how heavy a load I am pulling, and how hard I am working it.

Daily drivers driven in extremely cold temps (below say 20*) can benefit from the ability to warm the fluid with the engine coolant, but should have at least 1 aux cooler after the radiator cooler.. this will keep the temp more stable in the summer, and will help when towing or highly loaded.. in the winter, in temps below zero, I simply cover the factory installed and my second aux cooler with a small towel, secured by a couple tie straps. My 2001 suburban's 4L60E has had this done, and the current transmission is well past 300,000 miles, and still working perfectly. I rebuilt it at around 150K and like all of them, it had deteriorated due to overheating.

JW

 

So, it's the converter that's making the majority of heat? Burnt clutches and steels are from too many (too often) hard slipping shifts?

 

The inability to quickly and cleanly lock up the frictions, is what causes the wear and burning of the steels and discs, especially under power.

Most often, this happens when the lip seals on the pistons start to leak, as those rubber seals harden due to heat.

The result is a failed transmission, but the real cause is actually excessive heat, which shortens dramatically the seal and gasket life of the unit.

JW

 

I'm guessing a separate cooler and by-passing the heat exchanger in the radiator is the best way to go for a performance type car? Can the cooler be too big? There are a lot of cooler choices on the market. I plan on running a T400 SP (11") with deep pan.

 

Run the biggest cooler you can

 

Thanks, Larry, Jim and all others that contributed . Not my thread/post, but, answering some questions I've had. Yes Larry, lots of good info. I like the way you mounted the cooler, too.

 

I have some questions about my harebrained cooler mounting ideas! I can post this in a separate thread if this is hijacking too much . . .

My particular application is going to get a bit cooler heavy; I'm planning on a trans cooler, an oil cooler (for the road course), and eventually an intercooler (for turbos). I know most people simply mount their trans coolers in front of the radiators and call it good, but I feel that in my case stacking 3 heat exchangers plus radiator in the same place would be bad (just my feeling, not based on science), and be ugly. I was thinking of using 2 of these coolers for the trans and oil:

https://www.summitracing.com/parts/der-15840

Since I want to put the intercooler up front, I was thinking of either mounting them on the inner fenders with the fans pulling air in from the wheel wells through louvers, or under the car with the fans pulling air up toward the floor. What do you all think?

(P.S. I will get around to updating my build thread soon, I swear I've been working on my car )

 

Your feelings are correct!
Try to separate the coolers as best you can.
In order of importance (my opinion)
Engine cooling (radiator)
Transmission
Engine oil cooler
Intercooler
Being intercoolers are usually mounted in front of the radiator, try to mount the engine and trans coolers off to the side, that Derale dual cooler would work nicely and it can be mounted off to the side, out of natural airflow if needed.

 

On my 71 GS drag car I put the cooler below the heater core with some holes drilled in the inner fender to get some air, no fan. Never see temp over 140. I do also have a finned aluminum trans pan....

 

Thanks for the tips! Glad my intuition is correct haha.

I'm not sure how much of a sin it is to carve out big pieces of my inner fenders (I have one repo and one OEM) but I was thinking something like this might be a "cool" way to get air in:

http://rodlouvers.com/Pair-of-Aluminum-Hood-Bolt-on-panels-7-5-Straight-Louvers-Kit-P5496818.aspx

Not sure how much air louvers actually provide though. Maybe some sort of NACA duct would work too.

 

Don’t cut your inner fenders, yes you’ll get airflow, but also every rock, pebble, and piece of trash shot at your coolers not to mention your lower cowl area

 

Do you think some sort of grille/perforated screen would do the trick?