If it is a mechanical odometer then it is. Try resetting your trip odo and see if the main odometer works for awhile. What happens is the main gear on the odo shaft slips. I have repaired several but if you are not real mechanically inclined, I would have it fixed at a speedo shop. You can save SOME $$ maybe by removing the cluster yourself then taking it to the shop.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.