Extended hood or short hood??

That has nothing to do with it, geez.

 

Apparently you missed post #24. OP said when Peterbilt rebuilt the engine/truck they put it back to factory specs, which more than likely means it was castrated back to the torque rating of the the transmission, which as the OP stated was 1,400 ft-lbs. Please explain how upgrading the transmission to a heavier one and bumping torque/HP up will not help the OP's situation?

 

Im a little confused what year is this truck? How much weight are you pulling? Is it a 3406 with 425hp and 1450 torque? If so it sould have have no problems hauling tandem freight ten speed or not. Especially with 3.90 gears in it. That was a very common spec for years hauling more weight than that.

 

What rpm are you running at highway speed? And what are you pulling?

 

I still say if you get it right you will be happy with it.

 

Im with the others. There's an issue with the engine. Early e models cat can run 1500 all day long and get decent mileage. And at 1500 you should climb a lot of hills without having to drop a gear.