Grady_Wilson
Supporting Member
OP mentioned that he tried replacing the struts first thing with no luck.I think you have a bad lift motor. While you're replacing that, might as well replace the tailgate struts, too. They're cheap. Stabilus brand from Rock Auto are like $12 a piece.
You might try replacing the struts first, to see if that might de-stress the lift motor enough so it doesn't skip teeth.