You might also look at larger diffs when specing since your pulling large loads. While logging in the mid 80's I built a new Freightliner 12064 kit with 260wb. I equipped it with a 3412 ditta Cat with the then new large 18spd roadranger and eaton dtp two spd rears. Did a tremendous amount of Forest service off highway miles with over gross loads exceding 100k on five axles. Rated at 1250 hp it was detuned to 650 on the ground. With the horsepower we never needed all the gearing. Im not particularly familiar with all the new specs out there( Im retired O/O and SFO) but with the cats you will have plenty of torque to pull loads without winding the engines up. Caterpillars will pull down to the 1000-1100rpm range and hold. Many drivers are not comfortable doing it either from inexperience with cats or old school habits. Cats develop their peak torque in this range and the motor doesnt care whether it is in a truck or a large dozer. If the truck suits you otherwise and the price is right buy it, run it for a short time if needed and /or change out the trans with a reman or used from a wreck.the nice thing about an 18 is that it gives you that deep under set like a ten which you will actually rarely need with a cat anyway. but the 811 is truly underrated for anything but 10wheeler work where you dont need the hp in the first place. Who ever spec'd that combo was either cheap or (?)
