Speedometer Gear???

[MOPARJ]

As of late, the speedometer on my 76 slant six Valiant with a 4 speed has been acting up. I would hear ding ding like noises from the speedo and it would be bouncing all over the place occasionally. When you would come to a stop, it would usually stop on 10, 20 ,or 30 mph, not zero. Every once in a while, it would become less erradic, but it would still be 20 to 30 mph off. It progressively got worse. I recently ran upon another gauge cluster, which even though it had non functioning fuel and temp gauges, it looked better and I hoped the speedo would have been the problem. Once installed, this speedometer acted the same way. I installed a new cable last night, to no avail.

I am at a loss. Does this sound like a speedometer gear issue in the trans, or is it the new speedo, masking the real fix to the original problem, the cable. I cannot see two speedos doing the same thing, especially the one in better looking shape. The gear is the only other thing that I can think of.

BTW, I posted in this forum section, as I thought the speedo gear was relevant to the transmission section.

Thanks.

 

[adriver]

Here’s what I know.
Your Speedo is a close tolerance magnetic coupling. Two ears rotating around a disk.
Right? You should be able to see how this works.
Every speedo problem that I have ever seen is that the shaft is worn out allowing the ears to contact the disk.
OR dirt gets between the rotating parts and causes interference and the dreaded flopping needle. (The ears catch the disk).
You didn’t say if the “new” one stops on 20/30 too. In other words does it get stuck in the same place?
It is quite possible you got the “new” one because someone else had trouble with it.
They do give problems.
but I personally haven’t had a cable problem yet.
I’m not saying it hasn’t happened to other people.
But to me the cable either turns or it doesn’t.
Transmission drive gears? Well that would be some type of voodoo that I don’t know about.
Gears either turn or they don’t as far as I know.
I use LPS 1 and bench test the speedos before I go to the trouble of installing them.
It doesn’t attract dirt.
Just a little squirt on the shaft and gears. Keep it off the face.
I have a scrap cable end and use a variable speed drill to drive the Speedo.