I have a 2001 2500 Cummins with an Automatic transmission. I have no problems driving up hill without a trailer but even when I drive up a steep hill with a empty 2 axel horse trailer bout 16 ft long. When I go u the hill, I like have to floor it so it wont loose speed goin up hill. I have no problem on flat surfaces towing, its just goin up hill. I can go like a contansnt speed up hill but it only like 60. I dont now why it does this. I'm gonna have it scanned to see if theres anything wrong.

 

Do you have a boost gauge? Are you losing boost? Loss of power? Anymore symptoms?

 

I don't have a boost gauge, it drives just fine untill in the mph range, I towedit around with a horse and without one on the highway and up and down some hill at our ranch just fine, its just when the speed it high