[1976SaabEMS]

My speedometer stopped working, or rather it worked intermittently and now has stopped altogether. The last time it worked was after I hit a big bump on the road and it abruptly came back for a couple hundred miles but stopped again. I disconnected the speedometer cable and lubed it and tried to spray some lube in the back of the speedometer as well. It worked for a while and has stopped again. The cable itself seems to be fine as the odometer is working correctly. Does anyone have an idea what's going on? I know with the odometer there is a gear that slides out of mesh with another gear and that's what seems like going here as well, but I don't know the inner workings of the speedometer. Taking it out seems to be a big pain in the butt, so I didn't want to take it out unless there is an easy fix or at least one I can do myself. Otherwise, I'll live with no speedometer, like on most of the Alfa Romeos I have!

 

[jvanabra]

The speedometer is just magnet acting against a spring. Not much to break. I would double check the cable and the drive gear.

 

[Germaniac]

In the meanwhile, you could use a GPS speedometer just to be on the safe side.

Speedo cables can be tricky...you pull and lube them and everything looks okeydokey but once reinstalled they fail like before mostly due to a snag somewhere inside which only happens when the cable is in its old position again. And after 39 years, the drive gear can simply be worn out so it's probably the best solution to replace them both.

 

[AUSSIE900]

I note the odometer works so that would suggest that the drive gear ( gearbox end ) and the cable are functioning fine , I dont know what the problem is but suspect its within the speedo head .
cables that are binding/snagged can show up in a speedo head with the needle bouncing around ( as opposed Steady at the given speed)

 

[Cornbinder89]

40 years ago I could have named a dozen or more shops that repaired speedo's 20 years ago I could name a few, today they are few and far between, and parts are the problem. Either replace the head or go on a search for a shop that can repair them. They are not that hard to repair IF you have the parts you need, or can make them.

 

[wal]

I repaired my intermittent speedometer/odometer by replacing plastic gears sold by:
SpeedometerGears

 

[jvanabra]

The speedometer isn't gear driven though.... ?

 

[Cornbinder89]

Trucks just plain wear them out, If you get 1 million miles out of a mechanical speedo set up you are doing good, Electronics are good to 2 million or more (never owned a truck I put 2 million on). bushing can wear, thrust washers can wear, all change the alignment of stuff. Not rocket science, but more watchmaker, jewellry maker kind of work, if you have to make your own parts.
Many cars use a one piece cable which can transmit thrust force to the head, many truck set ups use a floating cable end at the speedo to prevent that from happening.
Point is: it is possable to make a long lasting cable drive speedo, but most cars aren't made that way and need parts after 30 years, you are on borrowed time. On the plus side, there are those that restore them and can make it good again, just not as many as there were 40 years ago.

 

[wal]

You might try contacting this outfit for a repair estimate: cluster repair

 

[Jim Mesthene]

First, while planning, squirt every nut and bolt you plan to remove with pernetrating oil, followed by a light oil such as ATF.
Doing this a month before you plan to start work is not too early. Doing it again 2 weeks later won't hurt.