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73-87 Chevy _ GMC Trucks => Interior & Equipment => Instrumentation => Topic started by: TheBigHat on February 04, 2021, 05:31:46 pm

Title: Speedometer
Post by: TheBigHat on February 04, 2021, 05:31:46 pm

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

Title: Re: Speedometer
Post by: zieg85 on February 04, 2021, 06:05:41 pm

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. 

Title: Re: Speedometer
Post by: TheBigHat on February 04, 2021, 06:38:25 pm

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

Title: Re: Speedometer
Post by: carmen77 on February 04, 2021, 08:50:26 pm

Quote from: TheBigHat on February 04, 2021, 06:38:25 pm

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...(https://uploads.tapatalk-cdn.com/20210205/94cbbcd9e77520d470a7295a032f4daf.png)


Sent from my iPhone using Tapatalk

Title: Re: Speedometer
Post by: TheBigHat on February 07, 2021, 11:11:18 am

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.

Title: Re: Speedometer
Post by: JohnnyPopper on February 08, 2021, 02:15:47 pm

You can also use toothpaste.

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

Title: Re: Speedometer
Post by: Chevygold on February 08, 2021, 03:04:22 pm

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