Rear Axle Gear

Rear axle ratio is very important. It directly affects torque, and that's what gets you down the road and up the next hill. My Ford F150 with the 5.4 and tow package has the 3.73 rear end. It works very well. Anything higher than that (lower number) is going to make the tranny downshift for often to compensate for the rear end ratio. I would not go below a 3.55, but would opt for the 3.73 or even 4.10 if you will be towing a heavy trailer and doing a lot of hills.