Gear Ratios

How much off road will you be doing?

Don’t know about logging, but I haul 140,000 lbs out of farmers fields. I have 3.91. Most guys have them here.
Can do 70 mph but usually do 62 mph.

 

3.90-4.33 should do it, easy on the clutch, and hopefully don’t blow anything else apart. Still able to run 70+

 

If you're only hauling 80k with no hills or major off road 3.70 would probably be fine. Lots of soft ground, mudholes, uphill starts, heavy weight I'd go 3.91 without question.

 

3.91s I'd go with for tall rubber. 3.70s would be geared a bit high off roading

 

3.70 or 3.90 either one will work fine with 24.5 tall rubber. Like is mentioned, off road, mud, hard starts etc, 3.90 probably best. But with an 18spd I would think you would be fine with 3.70. I have a Cat and Isx both with 3.70's and tall 24.5 rubber and gross 85-92k most of the time. I often load miles off the pavement at farms and ranches and come crawling out through ledge rock and low water crossings. Then on the other end of the trip it is 70+ mph for hours. Both trucks handle it all fine. Had a truck that was 15spd 3.90 tall 24.5 and it was just winding a little much on the interstate with no real advantage to speak of at low speed.

 

Tall 24.5s? If so, get a minimum of 3.90 if you have a 9/13/18 speed transmission.

 

If you want a work truck get the 3.91 if you want a road truck get 3.70

 

how much highway? I’d really look at even a 4.10 or steeper

our Tri axle has 4.56s with a 8LL and I can still get 75 out of it on tall rubber, let the pedal out and you are moving.