I ran my GV behind my c6 with 3.55 gears for almost 2 years. I had it set to engage at 55mph like a 4th gear. It made the c6 tolerable. I recently swapped to the zf5 and kept my GV. double OD running 85 im turning 2,000rpm. 18mpg. at 2,000rpm I would have to downshift to keep speed going up a large overpass/hill. Small ones were no problem. My truck is no power house, stock reman crap ip, ats 88 turbo (non wastegated). I would think turning lower than 2k you would be fine on flat ground. I think hills/overpasses would cause the trans to downshift.