We have a Freightliner Century semi hooked to a 39' steel hopper. We are normally grossing 80k. We only have about a 30 to 40 mile run to either elevator that we contract to, but have plenty of hills and curves leading to hill, so no getting a run for them. The truck has a Detroit 55 series 12 liter engine, that after I bought it found out it was actually made by Mercedes. It was rated a 365 hp, we took it to a shop to have turned up, but was told it had already been turned to max of 400 hp.

We like the truck, how it handles and rides. On flat ground it runs great, just that when you come to hills its a dog! There are a few hills that we are down to 20 mph to climb. We think it is geared high, it will run 80 mph if you want on flat. It has a 10 speed. I don't know currently what the rear end ratio is.

With that said. Any suggestions?

Thought about changing rear end ratios, not sure what that would cost. This is only a $8000 truck.

I go back to old saying " No replacement for displacement". Would a big block motor truck solve my problem? 14 liter, 450 hp enough? What rear end ratio?

I appreciate any and all suggestions.