Anyone know what the fix is and how hard? Thanks!

 

I had the same problem on my 73. Disconnect the speedometer cable from the back of the instrument cluster. Carefully pull out the cable. You will probably need a needle nose pliers to start with. It might feel tight part way out, take it slow. Once out, clean cable and lube sparingly with white grease. When feeding the cable back in, you might get some of the same resistance as with the removal. Again, take it slow. This probably is due to a curve in the cable casing. You may need to twist the end with the needle nose to seat the trans. end. A 1/4 turn at most should do it. Hope this helps.

PS: With small hands and removing the vent line, you can do this without removing the instrument cluster. Remember, I did this on a 73.

 

Could be in the cable,I'd try that first.Also could be a speedo problem.


Jason
VetteInstruments@aol.com

 

Speedo needle bounce can be caused by several things.

1) Speedo cable binding up in the car.
2) Speedo gear in the transmission wearing out, either the drive or the driven gear.
3) Speedo head first worm and magnet bushing failure

You can check the speedo cable by removing the cable from the housing. You can check the gear by removing it from the tranny

To eliminate the gears in the transmission, take the cable assembly loose from the tranny and attach a drill to it. If the bounce continues, then check the cable. If the cable is fine and you still have the bounce the problem is in the speedometer. If the bounce stops then go to the gears in the tranny.

The big question here is the odometer. If the odometer is not working then you have a failure in the first worm and magnet bushing. When this happens the gears won't align that drive the odometer and the first worm gear will eat the second worm drive gear up. The odometer then will stop working. Failure in the odometer is a warning that the head bushing is shot and the bounce is the magnet rubbing the speed cup ever so slightly.

If you have a speedo or mechanical tach in the car and you ever hear the tinging sound! Remove the cable instantly from the back of the gauge. The tinging sound is the speedo drive cup hitting the first worm and magnet. When you hear this noise you are not far from having direct contact or direct drive. Translated this means that you are about to slam the needle in to the cup stop below the face. The needle will usually break and cost you even more to repair.

Never "pack" the cable with grease! It is reverse wound and will push the grease in to the speedo head. A light coat of white grease is all it needs. Grease the cable, wipe it off and install back in the car. When installing the cable back in the case, be sure to wipe all excess from end of the cable housing end.

 

REDRED62:

That is the problem that I am having with my '77. The odometer isn't working and the speedo needle just sits there until I get up to an estimated 55-65mph, then it starts to bounce around. To fix the problem I need to do what?

 

All good suggestions, but if you have cruise, go there too. Might be the two internal disks have worn their bearings out in the transducer unit located inside the fender well.

 

I don't have cruise in mine so I think that it is the problem that REDRED wrote about. Now how do I fix it? Do I have to take apart the dash?

 

OK, here once again is the what is now the final definitive solution to this problem, my experiences/opinions should show up on search, but I leave that to other guys comments.....

of course the cable is the first thing, best solution is to force as much carb cleaner down the empty tube as you can, and let it sit in there, to disolve any grease tranny fluid dried up crap as possible....block the lower end, and then after about ten minits blow it all out from top side with air.....after that, buy a new cable, and install....OH,, one thing, make damn sure that O ring seal in the speedo drive gear is not leaking, that can shoot up tranny oil as previously posted....

also, you need know about the speedo head, there are two bearing sections about that thing, the most obvious is the bronze bushing section the cable fastenes into....fine, just lube/spary with WD40 and have over with it....but do it intelligently....

I have had to take apart many an olde GM speedo on the kitchen table, cloth, good light, magnifying glass if necessary, and study the damn thing....as you take it apart carefully pulling the needle off straight off...without damaging the parts...
now to take it apart further, and doing the obvious, and finding in there veary CAREFULLY there is an upper bearing, a needle bearing holding some of the compass card spindle...that thing is hidden pretty well, but a quick swipe with carb cleaner and some WD again....and reassemble...good as new....

that bearing grabs, and deflects the needle needlessly....

GENE