Originally Posted by 071crazy

Imo, I doubt that overdrive gearing would have an adverse effect on your engine. I ran over/underdrive gearing for a few gallons last year, and i didn't notice any overheating issue. Temp and humidity will affect your tune more than any change in load from overdriving.

Your center diff will thin out quicker, since the internals will be constantly working and heating up the fluid when all 4 wheels are on the ground.