Speedometer

[TheBigHat]

What ordinarily causes the speedometer to stop working on a 78 K20, 4 speed? Gear, cable or speedometer itself?

[zieg85]

verify odometer is not working either.  If it isn't pull the cable at the source and try to spin it.  If the cable spins but the speedometer doesn't the cable is broke. 

[TheBigHat]

Thanks. My cluster is so cloudy I can't see the odometer. I'll see if a drill with move the needle.

[carmen77]

Thanks. My cluster is so cloudy I can't see the odometer. I'll see if a drill with move the needle.

Here is a tip from a wise member  regarding the cloudy cluster...


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[TheBigHat]

Thanks, I was thinking of doing that but I've made them worse trying on a TransAm I had years ago and was afraid to after that. I know NOT to use Windex on them now. It made mine worse.

[JohnnyPopper]

You can also use toothpaste.

But look, you're going to replace it at sometime, so don't worry about making it worse 

[Chevygold]

Just been through this with my 76, disconnect the cable at the tranny, spin the cable anticlockwise and see if the needle moves, if yes the drive has failed which was my problem, the plastic gear had sheared off!
If the needle doesn't move when you spin the cable it could be the cable has snapped, give it a pull, don't go mad, and if it comes away that's your problem, if not it's probably the speedo head that's failed but they're quite simple and usually don't fail.
Hope this helps.
Graham