On my last adventure, temps were in the mid 80's and a good majority of the trail we were doing was in the sun. Lots of steep climbs, technical terrain done in 4lo and 1st gear.

I noticed a couple of times the dummy temp gauge in the dash cluster had moved slightly hotter than "middle" (halfway between hot and cold). I wasn't too worried, but that made me question--

As much as it sucks in warm temps, would running the heater (floor setting - no a/c pump engaged) help out at all?

 

according to the owners manual it does, I actually had to look something up in my manual and noticed it in there.

 

Are you running an additional tranny cooler?

If not... you might want to look into that. While I've not heard of any general issue with overheating in 4L, it does happen to the JK in 4H all the time. I've run mine in some extreme heat (days have run into the triple digits on occasion) without any overheating issues, nor have I noticed other JKs doing anything strange... I do run an additional cooler (exception: 4H hill climbs for those that haven't added additional cooling).