RCMAN46 wrote:
Changing the rear end gearing will not give you more power. It may allow you to pull a hill in a higher gear but in the end you will probably take about the same amount of time to pull a long grade and at near the same speed.
Only changes to the engine will give you more power.
I think the OP's question asked if changing gearing would make a difference to towing performance.
Take 2 pickup trucks identical in every way except for one having 3.73 rear ratio and the other 4.56 rear ratio, connect identical trailers - and set off over the same terrain. Which vehicle will have the easiest time towing, maintaining speed, and accelerating after climbing a grade with the least fuss?
(Edited to remove "class 8" truck comments.)
But on the other hand "high geared" tow vehicles (low number rear ratio) make great downhill haulers - they really go ... so you can make up time there...