Speedometer not working odometer working

[tattooboy37]

63 C20 3 speed manual transmission w/ column shift.

I haven't been able to figure out whats going on since the odometer works while driving but not the speedometer needle. Then when I pull out the cable from the tranny and spin the cable end it moves the speedometer needle.

Why one but not the other since both connections seem good.

Shouldn't the odometer not work if the gears inside the tranny weren't spinning the cable to move both it and the speedometer. I could see it being inside the tranny since I can get the needle to move by hand, but since the odometer works while hooked up that doesn't make sense. Plus I could see it being on the dash side if the needle didn't move while unplugged from tranny, but since it works that doesn't make sense either.

Please its been driving me bonkers.

[64tantruck]

I too have a similar situation on my 64 C20 my speedo works but my odometer is stuck at 62000. tenths advance but stays at 62,000 when it gets to 62,000.9 it rolls to 62,000.0 just happen last month.

Sounds to me like you have a broken gear. Not sure of the inter workings.

glenn

[tattooboy37]

From what I've read it just sounds like you need to remove the number cluster and lube it up. something is causing the next number to bind up.
I just cant figure why my speedo works by hand but not when hooked up to tranny. from what I have read both are turned by the same plastic gear in tranny.

[A.T. RockDriller]

Very puzzling.
I think if it was me, I'd remove the cable end from the tranny again and grind about 1/16" of length (max) off the inner cable.
Safe experiment..... and also may relieve possible binding.

Good luck.

[tattooboy37]

I'll give that a try, cant make things worse since I don't care if odometer works. I can always order up new cable and new gear mechanism if necessary. just trying to trouble shoot things and find out whats up.

[Dillon Rock]

I have a similar issue. When I bout the truck, the odometer and the speedometer weren't working but the needle was flicking, it smoothed out and worked again, then I went on deployment, came back, did it again and last night it decided to start working again. A guy I know at my local Car Quest says the cable shrinks over time and could be the culprit to our issues.