Tip is this .Never zero the trip on the speedo when your on the move.This is what strips out the pot gears and drives gears .. You can replace them ,,and all information is on DISEL GIANT web site Do a Google on it . I think there could be information on this site at the top. HOW TO ARTICALS I have repared a few speedos ,and the ones i have done the problem was the pot gear slipping on the shaft . Main thing is to tape up the tumblers to keep them all together .And to make sure nothing moves out of place .One vital thing is to lift the speed pointer over the end stop and mark the dial with a pencil in the place it rests .Then when you put it back on the speed should be right Any help needed,, pm me i may be able to help you. Thats if you do it yourself