hello got a puzzling question here..me and my friend both have pro 15 maxx's..mine has a new 2.5 tranny and im using the diff's from a pro 15 maxx..his has pro 15 maxx tranny and diff's..im running a 18 tooth clutch bell with the stock spur gear..he is running a 20 tooth clutch bell with stock spur..we both have the traxxas tuned pipe on them..here is the problem and they both do this in flat ground they have good top speed and look to be running great but when you try climbing a hill they just barley go like they are stuck in 2nd gear..and if you stop on a hill and try taking back off it takes them a bit to get took off..i have had pro 15 maxx's before and they didnt do that..any ideas what the deal is oh and im using a temp gun and the temps are 305 to 310