Trans cooling

212 is not all that high. By shifting into neutral when stopped in traffic you can lower the temp because of the torque converter slipping while stopped. I'd try that before spending any money.

For starters, 212 is a safe trans temperature. There is no reason to bat an eye at anything under 230. 165 is a little on the cold side in my opinion, but not damaging.
Adding a larger pan will keep a trans from heating up as fast (so it will not get as hot on a climb, but it is not the remedy for a loose TC that is generating heat all of the time).

There's nothing wrong at all with your temps and it needs to get up a bit to burn off moisture. Trying to lower it any more is just a waste of money IMHO.

On the freeway, does it lock into overdrive?

I'm not sure about the paticulars of your truck but once the torque converter locks up, the heat generated by pumping transmission fluid drops dramatically as it's no longer being asked to transfer power between the engine and transmission.

In city driving, the fluid is doing most of the energy transfer and that generates heat especially if you do a lot of hard acceleration.

Secondarily, in city driving less air is passing over the trans cooler due to slower speeds.

This is why you get a counter intuitive temperature reading with lower temps when you are putting out more power on the freeway.

You should be using Synthetic trans-fluid wnen towing since they removed whale oil from itanyway. It will handle signifintaly higher temps as well as offer better cooling charictics.

Moved from dinghy towing

I towed 11,000 with my 07 Cummins with the same trans in 100*F heat up mountain passes in Utah and my temps spiked to around the same. No need to worry. If it gets too much above 230* you might need to address it. FYI, the "TRANS TEMP" idiot light is set to come on at 260*.

The big reason temperature is higher in traffic is because the torque coverter is spending more time unlocked. As another poster said, slip it in neutral when waiting at intersections. If you have an EGT gauge, check the difference in temperature when idling in drive vs neutral. The temp will be slightly higher in drive because of the extra fuel being burned to overcome resistance in the torque converter. Some of that heat is going directly into the transmission fluid.

mikewats wrote:
I thought about installing a larger oil pan with an additional 4 qts. Has anyone done this with success?

I don't have access to Chrysler service information, but assuming your transmission pump pushes fluid through at a rate of about 1 gallon per minute at idle, and over 2 gallons per minute at 1,700 RPM , how long will it take to heat shear that extra 4 quarts? A minute? 30 seconds? Is that really long enough to make a meaningful difference when pulling a grade?

The temps you reported are OK, but if they weren't, any money spent toward cooling the transmission fluid would be better applied on hardware that cools the fluid you have, not hardware that adds more fluid to cool.

I installed a MagHytec double deep pan that held an additional 4 qts on my 01 Dodge. aside from the extra fluid, they are finned aluminum construction, have a larger surface area and will dissipate heat faster than a stock pan. The magnetic drain plug is also very nice. Expensive though.