ronjenx

I have the MOPAR cooler. It is a quick and easy install. No cutting and clamping of lines involved. It is more expensive than most aftermarket coolers, though.

Yes, the engine's fan will pull air through the additional cooler.

silverbullet88

Oh nice that's good to hear. Thanks for the info! I'll probably just go with the Mopar. You noticed a decent amount of temperature change?

rob_engineer

Another point worth discussing - the use of 4HI vs 4LO. The auto trans will be more prone to overheat when operating off road in 4HI. If you are going relatively slow, you should be in 4LO.

socal73

I was in 2 high when mine came on. Just a dirt/gravel road, not a lot of tire slipping but a pretty decent grade.

rob_engineer

I bet if you switched to LO the light would have gone out. The trans needs to do less work when the transfer case is in LO. The general rule I follow: on snow covered paved roads i use 4HI. When off road, I use 2HI for fire roads, then shift to 4LO if i feel the need to be in 4wd. I rarely use 4HI off road.

silverbullet88

You would think the vehicle should be made to handle the heat from driving in 4hi when lo isn't necessary. None have my Toyota's ever had this problem!
Although my jeep has never had the light come on.

rob_engineer

The addition of a trans cooler was the permanent fix. Does the Toyota have a cooler? Jeep made them standard starting with the 2012 model year.

silverbullet88

They sure do! Lol.

ronjenx

They used to be made to handle the heat. There was an engine driven fan that pulled air all the time. The transmission fluid was cooled in the radiator, which gave it a predictable, stable temperature.
Now, the water temp is allowed to climb pretty high before the electric fan comes on; too high for transmission fluid. So, with the pre-2012 JKs, they moved the fluid out of the radiator and put an external cooler, which was too small, behind the bumper. Not enough air could get to it.

They fixed that in 2012 with a larger external cooler, mounted in the direct path of air coming through the grill. I haven't heard of any 2012+ JK automatic transmissions overheating.

Like mentioned above, 4lo will reduce the amount of heat generated in the torque converter for a couple of reasons.
First, there will be less shearing of the fluid in the turbine.
Second, the transmission may get into 3rd gear, where the torque converter can be locked.