[697ibew]

Hello guys/gals,
I have a 70 Chevelle SS with an earlier Muncie (1964-65) with the speedometer exiting on the driver's side. The speedometer doesn't work, however, the odometer does spin. I haven't checked the calibration on the odometer but it spins and seems correct. Yesterday afternoon, I disconnected the speedometer cable at the trans and hooked it up to a cordless drill. The drill did move the speedometer needle off of its resting place and looked to stay "in ratio" with the drill. Meaning, that as I increased the RPM's of the drill, the needle would move higher. I believe the drill was in reverse, spinning CCW. I didn't do much else with the speedometer, as it was getting late, but I'm confused as to why the odometer would spin with the cable but not the speedometer. I plan on putting the car back on the lift and removing the bullet and driven gear to see if it is chewed up, but, I'm thinking it is fine since the odometer is working. Looking for some suggestions or ideas before I tear back in to it. Thank you all.

Jake

 

[blm]

I had a similar issue with the speedo on my 69. I switched from a Muncie with the speedo port on the pass side to a Legend with the port on drivers side. Well the cable was way too long. Being too long caused the cable to self destruct in short order. However it also chewed up the inside of the driven gear which I did not realize. I replaced the speedo cable with a correct length cable and speedo still didnt work but did work when connected to a drill.
Replacing the driven gear was the fix. Besides it may give you a chance to get the correct ratio plastic gear. yours is not original to your car and you still probably run a non capatable tire size + rear gears chances are the plastic gear is not right making your speedo incorrect.

 

[bry66]

That does seem odd!

Pull the speedometer gear and inspect the teeth on the gear. These gears are plastic so if the teeth are worn or if they don't fully engage with the ring gear inside the trans, then I suppose it's possible that the plastic gear might slip and spin too slow to move the speedometer needle, but still enough to turn the odometer. If the gear looks worn, just replace it. While you have the gear out, shine a light in the hole on the transmission and make sure the metal ring gear is centered in the hole.

 

[697ibew]

I'll try to pull the plastic drive gear in the trans tonight and let you guys know. Thank you.

 

[blm]

Take a good look at the adapter (plug that cable goes into) to make sure that is not chewed up as well.