Trans temp question.

I installed a trans temp gauge and the sender is in the pan. I daily drive up a grade on the freeway that's about 6 miles. The trans temp always goes up by about 10 degrees. I always shut the OD off before I start the climb. Is the trans temp going up on grades normal? I do have a auxiliary trans cooler temp installed. I have seen the temp get up to around 235 going up a long grade, the Grape Vine to be exact if any of you are familiar with it, and that was fully loaded with camping gear in the bed.

 

Yes, any time under increased load it will rise.

@gearcruncher has a chart with degradation of fluid based on temps. Lets see if he's around to share.

 

Yes, ATF temps go up on hilly drives. 235 is pretty high. And I don't mean to alarm you in that the actual ATF temps are probably higher. My 2nd gen Taco has two oem ATF temp sensors, one in the pan and the other monitors temps at the torque converter, which average slightly higher than the pan temps. To me 230 is the magic #. If my ATF reaches 230, I will do an ATF flush, which my truck hit last year on my trip Tx trip. I had read that at 230 the ATF starts losing it’s protective additive package. I upgraded my oem cooler to the slightly larger

$59 Hayden 679 Universal 11” Rapid-Cool Add-On Transmission Cooler to Enhance Cooling (not for direct replacement of the factory unit)

Hayden 679 and it has made a difference.

 

+1 on getting a bigger cooler. Pan temps are the coolest part of the trans. I have a temp sensor mounted on the inlet of the cooler which I think is more accurate. The ATF gets the hottest in the converter. 235F in the pan is probably 260F in the converter. I have the

$59 hayden 679 universal 11” rapid-cool add-on transmission cooler to enhance cooling (not for direct replacement of the factory unit)

hayden 679 and I don't see over 150F usually. Highest I've ever seen is 200F pulling up a huge hill.