Often I have wondered how much HP and torque can this tranny handle. I stopped in at the Allison shop today to ask. The book said 550# as the max input. These people couldn't say enough good stuff about this transmission. While I was there I bought filters at 7.60 each, an extra magnet for 3.19 and transynd oil for 30.03 per gallon. When I showed them the dyno chart for the Hypertech and asked if it could handle stage one they laughed. They said stage 2 is absolutely no problem and don't give it another thought whether empty or pulling the max load. By the way, the book also says max gvw is 19500# and the max gcw is 26k. My experience at the allison dealer was unreal. The parts man would talk all day, so would the service writer and ditto for the shop foreman.