Unregulated ATF Temps

[Ramblejam]

Something I've been thinking about as the temps drop...

Truck of mine is equipped with an OEM auxiliary cooler setup; transmission pumps fluid up to radiator end tank where the coolant absorbs heat from the fluid, then returns to transmission. However, this circuit is entirely unregulated, and is without any thermostatic control.

In the cold days of winter running down the road at speed (long after engine coolant is up to temp) -- TC locked and lots of airflow -- you'll have a very difficult time even getting the gauge to move off from 100°F.

With such an emphasis placed on ATF viscosity and frictional characteristics, how can this be an effective/efficient strategy?

 

[bullwinkle]

I've always read/heard that since ATF doesn't pick up moisture like motor oil does, cooler is always better-low temperature (within reason, above 0F or so) doesn't really hurt anything.

 

[nascarnation]

I think ramble is saying all this worry about fuel economy, etc why not have the transmission temp at a higher number for thinner vis and lower spin loss.

I will say many GMs have a thermostatic cooler bypass for the atf. My Cadillac with the 5L40 does.

 

[Ramblejam]

Originally Posted By: nascarnation
I think ramble is saying all this worry about fuel economy, etc why not have the transmission temp at a higher number for thinner vis and lower spin loss.


That's correct. I get that you don't want it running too hot, but how is continually running at 40°C an efficient thing to do?