I do not have time nor have i thought this fully out but ill post it while i have the time.
Transmissions in a car take the force created by the engine and transfer it to a corresponding gear which turns the back wheels.
Is it possible to replace the gears with a magnetic form of gears. This would stop the need for possibly at first poor gears, followed by gears themselves, then eventually the engine if the magnets could be set in a manner that the back wheels spin because of the reaction magnets have if they disagree.