The car had been parked for a few days and when I started it up to today the speedometer started acting erratically. At low speeds the needle is bouncing everywhere. After it shifts into 2nd, the speedometer in pinned at 200 km/h. At a stop, the speedometer is at zero but when I shift into gear the needle will pop up briefly before going back to zero.

I have had this happen before but after a few seconds, the speedometer would start working normally. Today this problem didn't correct itself. I don’t know anything about how the speedometer on an 85 300SD works, so any help would be great.

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1985 300SD

Your SD should have an electronic speedo...no cable. Sounds like you have a problem with the sending unit attached to the trans.

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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.

Sending unit is a simple a-c inductive pick-up sensor. The speedo itself(electric motor) is the most likely problem.

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Does to odometer work off of the same sensor as the speedometer? My odometer is still working. If it does run off the same sensor then I would assume it is the speedo that is broken. If it is the speedo, do I have to replace the whole unit or can I repair it? Is this a job I can do myself or do I have to send the speedo to somebody. Does anybody have any recomendations on who can repair it?

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1985 300SD