First I would check to see if that is what it is. Disconnect the speed o cable at the trans. Use a variable speed drill and spin the cable checking the needle on the speedometer. If the speedometer works fine, it is the gear in the transmission. If it doesn't then its the speedometer.

As for the gear replacement, I've replaced them on newer transmissions. Is yours a 3 or 4 speed?



David Gilmore
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1950 Chevy 3600