If you have adjusted the walking belt and drive belt, and neither of them slip. Then
You need a belt and deck. The drive belt should have nice clean ribs. If any of them are missing it will slip.
Be careful a worn belt and deck can blow your lower electronic drive board.
Change belt and deck together. I promise it will save you money.
www.mindbites.com/person/214-Mark
Mark Peterson, February 2008