warped gear
If your spur gear dosen't wobble on a T-maxx, it is because you have the slipepr all the way down(or your slipper pegs are different lengths like stated above), so basically if you aren't using your slipper, your truck will do wheelies, crank down that screw to tighten your slipper all the way... then you should be able to do wheelies. because those 2.5 motors should be able to lift it up, if not, maybe there is a manufacture problem, and get in touch with Traxxas, they are Really good in their customer service, maybe they will help you out.