Sounds to me like you are looking in the wrong place for the problem. Car is slow, batteries only last 5 mins, Lipo runs it fast but it burns up the speed control.... Sounds like you have something binding in the drivetrain. Put it on the floor and push it, does it roll ok? Hold a wheel in the side and spin it, does the opposite side spin freely? Hold the opposite side and spin the wheel, do the wheels at the oyher end spin freely? Take the pinion gear cover off and try to turn the pinion gear with your finger till the bigger gear has gone all the way around, is it tight?