This is something sort of new to my car. I have a fairly new rebuilt speedo and it has been keeping up with mileage for the last 6k miles. For some reason now the needle is jumping. There is an audible click and then the needle jumps so there is no real way to monitor my speed. I have the speedo out on the bench and was wondering if anyone has any good ideas on what to try what might be the problem. I have been using the short cable that goes to the odometer reset to drive the speedo and twisting it by hand on the bench. It will still make the click sound.

Any help is appreciated. :thumbs:

My first thought was the Tack - drive gear in the distributor - but you said it makes the clicking "on the Bench"

Is the end of the cable chewed up where it goes into the speedo housing?

Have you pulled out the cable from the housing and tried turning it that way?  That would eliminate any lubrication issues inside the housing. 

Lukesvette brings a good point.  If the end of the cable going into the speedo is frayed, even internally, then you can get a click from the cable binding up.

Alternatively, you could use a small bladed screw driver inserted into the speedo head and turn by hand to feel for a "click" or binding spot.

Since you have the head out, you could lube the head.  If it has never been lubed since, I believe the original lube was graphite.  If it has been lubed with something other than graphite, then it could be a chunk of graphite mixed with the liquid lube catching or a burr from the brass or lots of things.

I don't know of anyone around your neck of the woods that does speedos.  I found a great shop in Colorado Springs that only does non-electronic speedo & tachs.  I took mine in while on travel there and had him put a 140mph face on it and calibrate it.  It took him two days but it was well worth it and only $100 or so.

I can find his name and number if you are interested.  He is the third generation and it is a cool old shop.  I'd send it to him if it was mine.

I have the face and needle off now. The speedo was rebuilt less than 6k miles ago by a corvette gauge specialist. If it only last 6k miles from him, I think I can make it another 6k at least and save myself that wad of money.

Here is where I am starting from. Notice it stopped at 31000 miles on the dot. :thud:

http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01796Medium.jpg
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01795Medium.jpg

Here is the speedo with the face and needle removed. Just pull on the needle.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01798Medium.jpg

The bar across the front removed.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01799Medium.jpg
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01800Medium.jpg
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01801Medium.jpg
Eddie 702009-03-28 10:27:31

Okay, for those who may be following along.

Here is the speedo driven gear out of the speedo. It looks okay. It does have some small wear to it.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01808Medium.jpg

Here is the naked speedo head unit. I am not sure I should dig further into it yet. Everything inside seems to be working smoothly now and no clicking.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01802Medium.jpg
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01806Medium.jpg

Here is the trip odometer and its retaining clip removed from the head. This works smoothly and I suspect no problems from it. You can turn the shaft and the the miles will accumulate correctly.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01805Medium.jpg

Here is the odometer part of the speedo and its retainer. Now the shaft that goes through the center is free to rotate in both directions. I believe this to be correct. The driven gear on the end is what drives these numbers and it appears to be okay. Some small slight wear on it.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01804Medium.jpg

Another pics of the odometer with its "legs" taped to keep the together. I assume this is to make installation of the odometer easier. It appears that my tenths digit is frozen in place. Does anyone know of a way to free the tenths digit? I will keep plugging at it and fix it correctly or fix it till its broken. :laughing:
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01807Medium.jpg
Eddie 702009-03-28 10:30:04

http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01813Medium.jpg
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01814Medium.jpg
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01815Medium.jpg

Any good tips on how to get them out? It does not look like you can just pull on the ears.

I have been playing with the odometer. The only way you can add mileage with my odometer is if  you let the e-clip between the tenths and miles turn loose. Then the odometer works correctly adding mileage. This makes me think the tenths place has a problem. Am I going down the correct path.
Eddie 702009-03-28 10:31:35

Okay, I was trying to pull the "E" clip from between the tenths and the mile position and something clicked. So I decided to see what that meant. I tried the odometer and now it it working correctly. I don't know what I did now how long it will work. But I think I will keep digging and fix it more broke. 

rjent, thanks for the help on this one. I don't know what I did to free up the odometer but it worked. I could not stand it so I put the head all back together and tried it out with the drill motor. I ran it for 1.2 miles. So far so good. Only one problem, I forgot to put the ears back into position on the trip odometer and wound up with 111.4 miles. Go figure. Easy fix there. More pics

Here is the head all put back together and 00000 miles on it.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01816Medium.jpg

After running the head unit with my drill motor for 1.2 miles.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01817Medium.jpg

And here are the ears I mentioned earlier. Gotta get these dudes in place or you get crazy readings.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01818Medium.jpg

And here is the whole speedo put back together and ready to run again.
http://img.photobucket.com/albums/v399/Eddie70/Speedometer/DSC01820Medium.jpg Eddie 702009-03-28 10:33:37

Sounds like you found the issue. Good for you. I have had mine rebuilt twice and it works fine unless I try to reset the trip mileage. Then I have to play with it for a while to get it to work agian. I just don't mess with it any more.