I agree a good grease of the cable & the back of the speedo is first off. A lot of the bigger trucks had a little adapter on the outlet of the trans. to calibrate the speedo. Sometimes you have to take it apart & grease it inside. If the speedo was right before it should be right with the other head. All speedo,s were set for 1000 rev,s per mile.

They say money can't buy happiness. It can buy old Chevy trucks though. Same thing.
1972 Chevy c10 Cheyenne Super
In the Gallery Forum