Bypass radiator/tranny cooler combo?

Mark Kovalsky wrote:

Turtle n Peeps wrote:

I didn't disagree with Mark at all. I didn't know where his temps were taken and still don't for that matter.

When I was doing cooling tests at Ford I had anywhere from 50-200 thermocouples throughout the powertrain. I had thermocouples in the ATF line into the radiator cooler, out of the radiator cooler, and out of the aux cooler. I also had thermocouples inside the radiator reading engine coolant around the transmission cooler. I had about 20 throughout the trans so that I could map the temperature gradiant inside the trans. I had them in the radiator's upper and lower coolant hoses. I had a series of them mapping the air temp into and out of the radiator. I had them outside the trans to get an idea of the air temperature around the transmission.

Turtle n Peeps wrote:
Let me say it one more time. "If" ATF temps are higher than the ECT's "at all times" we are all in agreement.

I can't say that.

What I can say is that after extensive testing in ambients from -40°F up to +115°F I never found a condition where the temperature inside the radiator around the transmission cooler where the coolant was warmer than the ATF. ECT often was, but that's irrelelvant. What matters is the temperature near the cooler, and I maintain that it is ALWAYS colder than the ATF.

If radiator surround is cooler than transmission fluid, then I guess in hot weather it is doing it's job, cooling the transmission fluid. One thing that somewhat baffles me is using the radiator to warm AFT fluid at startup. radiator doesn't really start getting warm until the engine is warm enough to open the thermostat. by then in most cases I'd guess the torque converter slip has already warmed up transmission fluid, especially in any stop and go driving. and in the meantime your running hot fluid through a cold radiator.

Now maybe in extremely cold weather it will help keep the fluid warm enough once the thermostat opens, but what I've found on all the vehicles with transmission temp guages, the transmission fluid temps and coolant temps tend to track each other pretty consistently. Now they all have had the cooler in the radiator along with a big external cooler.