I've pulled my 31' travel camper for the first time on a 2 hour trip. Altogether it was a good trip. Pulls so much better than my old 2001 2500 HD 6.0 gas. One thing I did notice was after pulling a while, about 75 mph on an average, I would heard the engine "rev up" and I would lose speed. I would only lose about 5 mph in about a 3 minute span and than it would come right back up. I guess what I'm asking, is this normal for a diesel and if not any suggestions? Thanks in advance.

Were you in tow/haul mode? If not I'd guess trans slippage.

You may be hearing the engine fan. It sounds like a jet when the cluch engages. Did your RPM actually change or did you just hear different noise? As for the speed drop, the fan does rob a fair amount of power.

I agree on tow haul. Tow haul affects torque converter lockup. If the torque converter unlocks, your rpm will go up.

I'd also say cooling fan, it sucks alot of air and makes alot of noise.

Yep, I was in tow mode and the rpm's stayed the same. So thats good news. Thanks :cool2: