[blacknail]

Hey guys,
My '65 Mustang speedometer needle wobbles a lot so there's no way to tell what the actual speed is. What would be causing that?

[PerformancePartsInc]

Originally Posted by blacknail

Hey guys,
My '65 Mustang speedometer needle wobbles a lot so there's no way to tell what the actual speed is. What would be causing that?

The magnetic pole in the speedo itself is dragging or the speedo cable is freezing-up.

[blacknail]

OK. I'm new at this. Would you explain the magnetic pole? Never heard of one in the speedo cable.

[1967_Red_Stang]

Hey
I had the same thing happen to my speedometer after installed my new dashboard. Everyone told me to simply disconnect and reconnect the speedometer cable. I have not tried this yet, I will do it next week.
Hope this helps!

[Ivy66GT]

I have never had a Mustang speedo apart but it can't be much different than other ones I have worked on. In very simplified terms a mechanical speedo works because the cable twirls a little magnet inside a metal cup attached to the speedo needle. The eddy currents generated in the metal cup by the magnet cause the cup to turn against a small spring. The stiffness of the spring determines the speedo calibration.

The cup and magnet need to be close together so it all works but if either one gets a little out of alignment then they hit each other which will cause the needle to be unsteady. The magnet of this setup is the magnetic pole Jim was referring to.

More than likely its a bad cable causing your problem and sometimes disconnecting and reconnecting the cable will solve that - at least temporarily. However, I have had the magnet problem as well and was able to cure it on a antique Rolls for which there are no replacement parts.

[Icerat]

I have had much success with pulling the cable off completely and squirting something like WD-40 down into the housing. Let it sit for a few minutes then attach one end to a cordless drill and spin it full speed for about 30 seconds. Repeat the process with some white spray lube. This will keep the cable from sticking inside the housing which often causes the jumping needle. Also check the housing for a kink or cut into the metal that could be catching the cable inside. Hope that helps.

[The Greek]

I agree that your problem is in the speedo cable lacking lubrication. The cable needs to be greased by removing it from the outer portion (Jacket) and applying grease to its whole length. White lithium grease is the type that is preferred.

It's also a good idea to inspect the Nylon driven gear that is on the transmission end of the cable.

[phillipcm]

You didn't mention if your speedo had worked correctly in the past but if all else checks out, you may have the direction driven gear on the end of your cable. Depending on what type of trans you have, there are a LH or RH driven gear. Unknown to me, I was using a LH driven gear on my toploader. My speedo needle bounced all over the place. Once I figured out I had the wrong gear, I ended up changing the driven gear and the drive gear on the trans output shaft because it was trashed after trying to mesh with a gear whose teeth were cut in the opposite direction. Hopefully your problem is a simpler fix. Good Luck!!

[blacknail]

Thanks, guys. This is a car that came to us from a neglectful owner. goodness knows how it acted before I got it. I'll get at it, I appreciate the advice.

stay well!