I went with the GM 2500 with the 6.6 gas engine and the Allison branded transmission this truck is very reliable. The previous post about the same tranny where thinking 1/2 ton trucks. The reason I went with this truck is reliability and cost to own I did quite a bit of research and would have bought a tundra if they still had a V8 but I wanted to stay away from the extra maintenance of twin turbo's down the road. The LS style motor has been good the 2500 has no AFM are DFM which helps in reliability, the Allison branded tranny has worked well behind the diesels and the rear differential is bullet proof behind the 401HP engines. I get about 14 MPG average so for only 3 trips to the lake.