Looking for opinions here. The speedometer in my ‘64 hasn’t worked since I acquired my car, the clip fell out of the drive gear in the Muncie and I never got around to fixing it. I sent my cluster out a few years back to Roger Scott at Corvette instruments to be refurbished. He mentioned that my speedometer looked good as they are often chewed up inside. That made sense since mine hasn’t worked in years but of course I couldn’t verify that it worked back then because I never fixed the gear inside the trans. Last year, I replaced the chassis in my car and put a five speed in from a Camaro. Now that my speedometer is working, it seems OK until about 40 mph and then it starts to swing back back-and-forth by about 20 mph and gets worse the faster you go. I realized that when I put everything back together I neglected to lube the new cable so I just took it apart and greased the cable with synthetic grease. It seems better but still swinging. I just used an ordinary cable from the auto parts store. I’ve since seen some discussions on here that cable quality can be an issue. There are no sharp bends in the cable. Does that sound to you all like an issue caused by a cheap cable or faulty speedometer? I would hate to send the speedometer out for an expensive overhaul to find out it was a cheap cable but would also hate to go through the trouble of pulling the cluster and replacing the cable only to have to pull it out again and send out the speedometer. Anyone have a similar issue? Thanks in advance!

 

I would suggest disconnecting the speedometer drive cable at the transmission. Chuck the end of the drive cable in a variable speed drill (and I believe you have to run the drill in reverse) and gradually bring the speed up while having somebody watch your speedometer needle to see if the bounce occurs. If there is no bounce it is probably not the cable. If it is not the cable you may have a mismatch in the size of the drive gear inside the transmission and the driven gear on the end of the speedometer cable. In that situation you can have the driven gear just barely touching the drive gear and it can result in swings in the speedometer reading. If that's the case the driven gear will eventually wear to where it won't register at all. If you know the rear axle ratio in the Camaro, you can determine which driven gear would be appropriate. Otherwise you may have to try some different gears..

 

I didn’t mention that when I first put it together, the trans had a 22t driven gear which was as installed by the factory (trans is from 1987 Z28) and the Speedo was about 6mph fast (and did the bouncing above 40). I switched to a 24t driven gear and now the speedo seems accurate but still swinging so I’m fairly sure it’s not a gear issue. I can try the drill trick but if it’s still swinging with the drill I still won’t know if it’s the speedo or the cable that’s the issue.

 

At the transmission, turn the cable with your fingers and feel for any roughness. Also push the cable in and out to see if there is any movement as it may be too short at the speedometer end and not fully engaging the square drive in the speedometer. Have someone watch the speedometer as you do the same thing with the variable speed drill in reverse slowly increasing to maximum speed of the drill. If you have don't have a smooth cable operation, disconnect it at the speedometer and spin it in you fingers to see if you have smooth operation..
If you have the original cable, compare the length of the square drive to the stop on the cable.
Only recommendations I have to help identify the problem.

 

I guess I will start with the cable - it turns smooth but seems to require more effort than I would expect even when disconnected from the speedo. Any recommendations on who offers a better quality cable than the standard auto parts offerings?

 

Deluxe Speedometer Repair & Cable Services in Colorado...the absolute best.
https://deluxespeedometer.com/

 

Thanks Leif. Do you recommend them for a speedometer overhaul as well if the cable doesn't fix my issue?

 

I just sent them the speedometer and tachometer from my 63 and also both cables to inspect.

 

if they’re cable is disconnected at the transmission then you should not be able to move the cable in and out. There is as attached (usually brass) ferrule that prevents it from moving in and out very much. It will move in and out at the transmission end.
if they’re cable cable when disconnected at both ends is stiff when turning by hand, pull the cable out, clean it and re-lube it with CableEase. If they’re cable cable re-lube doesn’t work get a new one from the above mentioned supplier, there’s none better than theirs.

Don

 

Yes...

 

Of course you are the only one that can feel the drag on the cable when you spin it in the sheath, but it could be just lack of lubrication as the friction between the cable and sheath is increased in the bends required to get to the speedometer. If the cable is dry, you may want to lube it before getting a new cable. Some recommend not only a new cable, but also a new sheath, but I don't really know how to inspect the inside of the sheath for wear to determine if it also needs replaced.
For years, I have used dry graphite to lubricate the cable, and I have also used CableEase. As the CableEase has a grease in it, it may last longer.
Ron

 

Sorry, when I say 'cable' I mean the inner cable and outer sheath, it was purchased new as a complete assembly. I lubed it with some synthetic grease, it feels smooth but requires more effort to turn than I would expect. I converted my car to a 5-speed so I will have to measure the length prior to ordering. As mentioned earlier, I don't have any abnormally sharp bends in it.

 

If you tried the drill at the transmission end and checked the cable movement in and out and it still bounces, it is likely either the engagement of the square end of the cable in the back of the speedometer or the speedometer gears. Just my guess. If you have your original cable, you could compare the projection of the square drive beyond end of the cable. You might also hook the old cable up in the cabin and spin it with a drill.
If all else fails and you pull the speedometer, test it with the drill before shipping it out.
Assuming the driven gear at the transmission is good and the square drive socket is the same size as the GM drives for the 60s transmissions.
All guesses.