I had a similiar problem with a viper that I put a 144 on. The problem turned out to be binding the track due to geometry changes. What was happening was as the suspension would compress it was trying to stretch the track, ie. the suspension was getting longer. try putting a block under track and check the track tension with you on the sled. I was also getting only about 2-3" of travel. I had put a big wheel extension on it, and it just didn't work. I ended up putting a mountain suspension in it (new rails, h-arm, etc.) Works great now, but it really had me going for a while. Hope this helps.