My speedometer stopped working about 6 months ago and I determined (with the help of the forum) that it was the lower speedometer cable. I slid the cross member back and put in a new cable but now the speedometer is bouncing all over the place +-30mph when I am going down the road. Did I put it in wrong? Will it smooth out eventually? Thank you.

 

If the speedometer cable has any sharp bends in it it will bind. Did you lubricate the cable (inside the cable housing) before you installed it?

Either way what you are describing sounds like the cable is binding then releasing, causing your speedometer to indicate the same.

Do you have cruise control on your car? There is another short speedometer cable on C/C cars that goes from the C/C transducer to the speedometer.

 

When I replaced the speedometer cable, I had to pull the cross member to get to the connection on the transmission. I thought I did it right. The cable was already lubricated. I have a feeling it stripped something out because it does not work at all now. I am going to look at the cable going from the C/C to the speedometer first and see if that one is bad also.

 

Might check the plastic gear teeth.

 

There is a plastic drive gear in the tail of the transmission that the speedometer cable engages. The gear might be bad.

 

I am going to change the plastic gear but before I pull the cross member and everything, do you know what color gear I should get. I assume that the tranny and rear end are stock.

 

Forgot to mention it is a 1979 L-48 and it has original rims and tires also.

 

We had the same problem (bouncy speedometer) in a 1970 Corvette just a few weeks ago. Replacing the cable and housing (no easy task!) did NOT fix the problem. However, after speaking with a gentleman at D&M Restoration who was familiar with this symptom and cause, we removed the speedometer (also no easy task for the unexperienced) and took it to him. He did a fantastic job restoring it (and the tach) and that fixed the problem. The internal gears of the speedometer were severly worn and the internal bushings were brittle and broken (we were given the old internals). He replaced all of that and when we reinstalled it it works smoothly once again. So, as hard as it is, you may want to pull the speedometer and send it to them. They are online at...
www.dandmrestoration.com
800-722-0854
They are great guys over there. When we were there he had just finished restoring a beautiful Rolls Royce instrument cluster and housing that seemed to weigh about 10 pounds. They can re-image the instrument lettering, too, if it needs it.

Good luck!

 

I put all the transmission/speedometer gears on order from Wilcox Corvette and I will install them when they get it. If that doesn't work, I will look into what DouginSC did and get the speedometer done. I will let you know how it goes.

 

Discovered the problem with my jumpy speedometer and eventually the broken cable. The cruise control was froze up and would not turn so it kept breaking the cable. Removed the cruise control module and ran a speedometer cable from the tranny to the speedometer. Works great. Thanks.