3.91 vs 4.31 for up to 80K lbs

Only 80k you'd be fine with 3.91s. Hell my old man drug 118k out of the mountains with a 530 ISX and 4.10s with no problems.

 

4.30 will give you a bit better grunt out of the hole though.

 

550HP? 3.55s-3.70s. 4.30 is way too low. Overkill for 550HP. Like a big dog on a short leash. Leash is so short that the dog can't exercise. Heck, if you're staying under 80k, 550HP would pull like a champ with a 3.33 or 3.55 ratio...especially if backed by a strong 18.

EDIT: The only way I'd rock 4.30s with a 550HP engine is if I had plans of pulling 160k GVW.

 

3.91 is most common for us pulling 140,000 lbs on the prairies.
Mountains 4.11 more common.
4.33 for forestry work.
Anything beyond that is more oil patch, off road work.

 

Yeah 4.33s with a modern RTLO 18 speed on 24.5 rubber you're going to be tach'd out at around 65ish too lol.

 

bet thats like 1650 rpm tops.




in my area local guys run 76.5k on triaxles: 3.90 for highway trucks mostly, 4.56 for local/off road trucks.
All tall rubber, all 18’s, all 550+

riding to your destination a little slower may be frustrating- bet the first time you get a tow from a few miles out in the woods would be more so.

@Tim4788 do you know anyone that does the kinda work you'll be doing from around your way? Be a reasonable start to ask someone that’s doing it in the same area what they use n go from there.

 

Yep you are correct on that one.