Car is running too warm

I live in the Mountains where it's cooler. I just started working down the hill. But when I come home even after it's a little cooler. My Trans Over Temp light comes on, and my transmission is revving a bit and not shifting properly. I end up turning the heater on full blast to cool off the engine compartment. I took it to a mechanic that said it's running at the proper temperature but my problem hasn't shown up before I took it in. I have a donor car the same configuration. What's the chance that torque converter is bad. Just afraid this is going to be so expensive. But I don't want to kill my engine or transmission. Car has about 123k miles. TIA

 

did the mechanic check for codes? Post all codes.
has trans been serviced - fluid (ATF4) ONLY !!! not universal.... and BOTH filters?
were engine cooling fan checked?

a thought on converter ---the slip would likely set a DTC.... and reasoning enough for a SCAN

 

Welcome! So the mechanic was not able to replicate the issue with the transmission nor comment about the Trans Over Temp warning light? Auto parts shop like Advance auto or Autozone usually offer scan service. Post them for assistance.
With all the warning signs from the Jeep this needs to be addressed promptly. If the temp issue is only with the transmission then there may be blockage at the auxiliary transmission cooler and/or lines.

 

aggrex made me remember

there is a cooling bypass valve in the cooling lines to transmission very very offten they fail and it fails closed

 

Thanks Chris! Happy to be here. Well sort of.