I have a 89 gmc sonoma 2.8 there was a converter box between speedo cable and trans. It broke and dash is now off by 15 mph. What is the part called and were do I find one
It is called a speedometer transducer box, if you can't get one from the dealer try looking for a good used one with the same ratio or take yours to a speedo repair center and they may be able to rebuild yours. It won't be cheap. i worked at a speedo calabration shop and we made these up for hotrodders at that time it ran 120 bucks for the box and gears and another 70 for labor.
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