The speedometer on a '75 like ours is mechanical. The "failure point" on the odometer is a metal gear that slips on the main axle that holds the numbers. What I had to do on mine was to use a pair of diagonal cutters with stripping notches to create a couple of notches and squeeze some metal outward that got the gear to grip much tighter.

If you need further info, P.M. me. Depending on where you live in the Valley, we may be able to meet up, I'm in Glendale.

Scott

__________________
Remember, it's not just a car. It's an Adventure.