my chevy is a 02 6.0 with 4.10's I haul right at 10k with mine and I just don't keep the pedal to the floor going up hills. we have a fairly good hill here in eastern Oregon and I keep my truck in 3rd gear and around 3K rpm's going up. that is plenty fast enough or me, I even pass the semi's the 6.0 with 4.10's is a brute in my opinion