set up

A 12.7L motor is rather small for running 120k...especially with 3.25 gears in the rears. And those 40k rears won't be sufficient, either...you'll want enough rating to be able to lift your tag at jobsites and such where extra traction is needed WITHOUT overloading them.

And yes, spec'ing a truck too light will cause premature failure of those under-spec'd components.

 

It’s not ideal but it’ll work. There are PLENTY of construction companies running trucks speced lighter then that hauling heavy all the time including us. Our spare is a 97 T800, 3406E 455 HP, 13 speed 40,000 rears with 3:70’s and a single frame. I can promise you it’s had s lot of abuse. Take it easy and it’ll get you by.

 

That's a 15L engine, not a 12.7L...and 3.70 gears, not 3.25's. Big difference.

 

I don't do heavy haul myself (truck isn't spec'd for it), but I wouldn't even run the freight I do with the specs you were looking at. To put it into perspective, I've got a 728ci Mack (12L) engine, with 485hp and 1660 ft lbs of torque. That's run through a Mack 18 speed and 38K Mack rears with 4.17 gears and 11R24.5 tires (equivalent of 3.70 gears with LP22.5's). When I pulled bulk freight (pneumatics & end dumps), I'd shoot for 80-82K. I wouldn't run a lighter spec'd truck for legal freight, let alone playing around with the heavy stuff.

 

Yep I’m aware, still 600 horse, first construction company I worked for had a 12.7 430 with 3:55’s and it was around until a couple of years ago. Used to be a LOT of 350 Cummins around pulling big loads. Is it ideal long term? No but it will certainly do the job until you can figure out what’s going to work best.

 

On second thought anything above 80,000 you better get one of these.

 

Isn't that the load that was sitting on the side of 95 because they started without permits??