Which Differential for Truck Camper

I'm pretty sure we all know this but differant rim sizes generally come with standard tire sizes from the factory for the particular rim size. With an 18" wheel you can not get back to the diameter of a 16" tire unless you want a wheel tire combo that closely represents a roller skate.

Bottom line is you need to take TIRE size into consideration when selecting a differential.

rooney77 wrote:

FreeLanceing wrote:
373, you could even probably drop down one more gear if it was an option. It is an option in the 1/2 ton. The lower the gear the better the fuel economy period. I know a guy that tows a heavy fiver and he has 2 sets of gears. He runs the high gear 6mo. About April or so he brings the truck in and and has the tow gears installed. Must pay off or he would not do it. I guess it depends on where you live and what you do, but here in the midwest 373 would be a good allaround choice. These new gas motors put out so much power, coupled with a 6 speed, they can handle most any situation.

When you say "lower" I hope you mean numerically lower. Generally a 4.10 is considered to be a lower gear than a 3.73. And a 4.10 will have the motor revving at a higher rpm than a 3.73 at a given speed...which means worse mileage.

llavaseur wrote:
Tire size has to be taken into consideration.

Comparing my previous 2008 silverado to my new 3500 silverado both with 6.0 liter this is what I get/got.


these 2 configurations perform great, no complaints
2008 2500 silverado with 3:73 and 245 75 r16 tires 1975 rpm @ 70 mph
2014 3500 silverado with 4:10 and 265 70 r18 tires 2050 rpm @70 mph

When I ran my 2008 2500 silverado with over sized tires listed below the power band was way off on inclines it needed to down shift so low the motor was screaming at expressway speeds, I did not like it.

2008 2500 silverado with 3:73 and 285 75 r16 tires 1750 rpm @ 70 mph
(my only complaint with this confiruration was inclines at expressway speed)

when you compare the tire diameter of 265 70 r18 and 285 75 r16 it is within one quarter inch.

So my conclusion is your tire diameter should dictate your gear size, I would not run a 3:73 with 18" wheels and and I would have to think long and hard weather I would run a 3:73 with 17" wheels.

Why would your rim size determine gearing? Tire OD should determine gearing, the rim diameter really would have no effect unless you're nitpicking weight.