I have a 31 coupe with about 15,000 miles on it se
Remove the gear/case assembly from the bottom of the torque tube and make sure that the drive gear on the drive shaft is not sliding back and forth. There should be a snap ring on the drive shaft that keeps that gear from moving too far. If the snap ring is there and just moved forward from the groove, you can take a screwdriver and pry it back into position. If all is OK there, be sure your cable is well lubricated. It should be lubricated with a graphite grease. We offer this grease as part number A-17260-L. If all checks out here, the problem could be in the speedometer itself. It is best to just exchange the speedo for a rebuilt unit if that is the case.