Hey everybody. I have a 69 Cutlass that I use as my daily driver (when the streets are clear and dry). Recently my speedo has gone belly up. It behaved as though I had a bad cable. The old bouncing speedo. +/- 3mph where you can guess your approximate speed by averaging the bounce. Plus it sounded pathetic. So I bought a new cable and installed it. Oh I forgot to mention that it was much worse the colder it got outside. Anyway, after the install on the new cable, I still have the bouncing speedo and the horrific sound. So now I'm leaning to the speedo itself. My question is, has anybody here ever disassembled and repaired their own speedo? How bad can it be? It's basically a transmission right? So many revolutions of the cable result in a given speed. So, anybody? Thanks.
Kevin

 

Hi Kevin
If your up to the challenge I'd encourage you to try fixing it. Then tell us all how it goes. If you strike out and have to toss your bad one there's probably several people on this site with spares, including me. John

 

Have you double checked the drive gear in your transmission? That would be easier than tinkering with the speedo. I think you can access it by removing the transmission tail housing.

 

That wouldn't make the noises he's hearing though.

 

One thing that often happens is that the cable goes bad (resulting in the noises) and the added friction from the cable causes the plastic gear in the trans to be damaged. Don't ask me how I know this...

 

A speedometer is actually a small magnetic induction motor. The cable spins a magnetized cage in the housing which is not physically connected to the needle. The spinning magnets induce a field on the needle causing it to move. Faster the cable spins, the more movement is induced in the needle.

If a speedometer is WAAAAAY off, the magnets in the cage may have gotten weak. A speedometer shop can remagnetize them and lubricate everything and get it just about dead accurate.

 

It sounds like the cable is binding in the housing or you have a messed up drive gear. If it bounces faster with the speed of the car it's almost always the cable.
Did you pull the cable out of the housing and lube it with white lithium grease before installation?
It should turn freely in the housing with no binding at all.
No real sharp bends or turns?

 

I'd first be sure the cable is well lubricated

 

I agree with all said above. It does tend to indicate the cable even if it is new. It is much simpler to remove the cable and re-lube it to be sure. Thanks everybody. All I have to do now is wait for a day to do this. I was curious to get into the speedo and see what made it tick, but if I don't have to, I can live with that as well.

 

I need a speedometer for a 66 Olds 98 if anyone has one. Thanks.