Gear swap?

[kodiakoutdoors]

Has anyone changed out the differential gears on the D/A or have any opinions about this?

[DmaxMaverick]

My brother had a 2002 HD 8.1/A with 4.10 gears. He hated the low gears. No mileage. I went up to 33" tires on mine and thought about swapping rear ends with him. He would have higher gearing, and mine would have near OEM final ratio with the larger tires. That was before I towed heavy with the larger tires. Towing at about 22K GCW, I didn't notice any remarkable loss of performance. I tossed the Idea out the window and he sold the truck.

Unless you are having problems with your current ratio, it's probably better off like it is. There may be some advantage to going with a higher ratio (lower number) of you don't tow heavy. It's not likely that you'll gain enough to offset the cost.

[kodiakoutdoors]

thanks for your input. i don't know what my final gearing will be, but i will be running 37" tires. i don't tow anything, but i do carry heavy loads in the bed. i guess i'll just wait and see how it works out. thanks again.

[JimWilson]

While the rear end ratio will only be "effective" -- not actually changed, but seemingly so -- you can do that math yourself and find out what the difference will be. Try using the following formula (note that the sizes are in inches):

orig_tire_size / new_tire_size * rear_end_ratio

For example, in my case I went from a 245/75/16 (30.7" diameter) to a 285/75/16 (32.7" diameter) with a 4.10 rear. So, what's my "new" ratio? It's 3.84 (30.7 / 32.7 * 4.10 = 3.84)