There is a tranny cooler on your truck. The manual says that it's standard on all engine packages and is located above the power steering cooler on the front of the radiator. I went out and checked mine and sure enough it is there. The lines come in from the passenger side. The power steering lines enter from below on the drivers side. These 2 radiators are sandwiched in between the AC radiator up front and the coolant radiator so they will be hard to see.

Just a question, you have checked your fluid level?

 

My Trans temp does not seem to go above 69 Celsius with hard driving. Otherwise it seems to stay around 56 to 58 Celsius during normal driving.

Fluid levels are all good.