Hello Gene, I've got a 2015 Chevy 2500 HD with the 6.0 and 4.10 rear 4X4 and tow a 2015 Forest River 33 ft. fifth wheel. It grosses out at around 13000 lbs. and yes, it sucks gas but has no problems going up the hills. 42000 miles and no problems yet and it ri... Login to read more.