My speedometer started jumping around on my 1966 Mustang. Then it would stop for awhile and jump wildly for a while. I took it to a shop where they put in a new speedometer cable. It still jumped wildly and now it stopped completely. Suggestions?

 

This was happening on my 4 spd and it turns out that i had the wrong gear on the cable. The 4 spd uses a different speedometer gear then the rest of the trannys. That might be a place to start.

http://www.johnsmustang.com/Catalog-740.html
Here you can see the difference in the two gears

 

That happened to me. The speedo was jumping badly and the odometer would not work. I had a shop put in a new cable and it was just about as bad and then stopped working completely.
Turns out they did not get the cable seated in the rear of the speedometer. It's almost impossible to do from under the dash. I took out the instrument cluster and got it seated well and it's fine. I did have to free up the speedometer some though. It was binding. I did that by manually spinning it with my fingers while it was apart. You can do that by removing the speedometer from the instrument cluster. Be careful, it's pretty fragile once it is out of the cluster.

 

It could be the wrong gear or a damaged gear on the trans end of the cable or the cable itself could just need to be replaced or lubed.

It could also be the speedometer itself. Thats what my car needed.

 

Speaking of speedometer issues. Mine has a small issue that I don't know what would casue it. It works correctly almost all the time. Occasionally at speeds around 35-45 it will be a little jumpy or wobble. What would cause this? It has all new components.

 

better check the speedometer itself....

 

My speedometer and the entire instrument cluster is new.

 

GibMax,

Pull out the gear from the transmission and see if it is chewed up. If it is, then it is likely that the spiral in the transmission is buggered up, cutting the plastic gear. Also check to be sure that the replacement cable was cut long enough.

tx65,

It is highly likely that all you need to do is lubricate the cable. To do this, get some speedometer cable lubricant from the auto supply. You can use synthetic motor oil in a pinch. Regular oil will gum up over time, but synthetic should not. Unscrew the thumbscrew on the back of the speedometer and then pull the cable out of the housing. Put lube on the cable liberally while feeding it back into the housing.

Lubing the cable before it gets worse will usually prevent further problems from ever developing.

Doc

 

This gets asked all the time and I have never gotten a good answer. When I go to Napa, AutoZone, or Advanced Auto and ask for speedometer cable lubricant, they just stare back at me. If you do a search on google, you get a bunch of trash. What make and model stuff do you use??? The only stuff I have ever used successfully comes with some of the speedo cables, but I cannot find it a-la-carte.

 

I used the stuff that was kind of like grease that came in a little packet, It came with the cable.

I have this but wonder if it is any good. It says it graphite.

http://www.paddockparts.com/Paddock/...285D38E5AA7D21