Speedometer Cable Problem

[Jimmy Vette]

My 1980 speedometer quit working. I checked the upper cable by disconnecting it from the transducer & spun the cable. The speedo worked fine. I then disconnected the lower cable at both the transducer & the trans & it spun fine as well.
I noticed that the end of the lower cable, at the transducer has a nylon end. I am not sure what this end should look like, (it is sort of rounded off) It looks like it may be stripped. I have two questions. Is it is stripped why would this happen? Is is possible that the transducer, lower end, is somehow frozen up? Should it spin freely? Seems like it is spring loaded. I guess I am looking for some advice on what might be the problem. Thanks all.

 

[jz7p6t]

Could be Speedo Gear in Trans!

I had a similar problem on my '80 Vette, Speedo inoperative. I disconnected the Speedo cable at the trans and spun it with a cordless drill while my wife watched the speedo. It worked fine which meant the speedo drive gear or driven gear were no longer turning. It's easy enough (more or less) to remove the driven gear and inspect it for damage. Also see if you can turn the driven gear that the speedo cable attaches to at the trans. You might need a short piece of speedo cable as the gear has a square hole for the cable. If you can turn the gear then your speedo drive gear has come loose or the driven gear is damaged. The problem on my '80 was that the Speedo Drive Gear on the Trans output shaft had come loose because the retaining clip had broken! You can buy new gears/retaining clips from TCI automotive. I hope this is not your problem as you have to remove the exhaust, driveshaft, trans crossmember and trans tailshaft housing to fix it.

Good luck and let me know if it was the same problem.

 

[john1977]

Had a problem on my 77 last summer like you describe,found out the gear around the output shaft that drives the gear the cable goes in had lost its retainer clip. At times the speedo would work then it wouldnt. Every time I unhooked cable at trans. and hooked it back up it would work for awhile then quit. If this sounds the same,let me know, its not that hard to fix,just have to pull the tailshaft off, about a 30 min, job.
Good luck

 

[Jimmy Vette]

Thanks for the info...I ordered a new lower cable just to be safe...should be here on Monday. In the mean time I had a look at the trans and I am not sure how to pull the tail shaft off. All I can see is the treaded end sticking of the trans. Does the whole thing screw out or can you some how pull out the gear?
Thanks again.

Had a problem on my 77 last summer like you describe,found out the gear around the output shaft that drives the gear the cable goes in had lost its retainer clip. At times the speedo would work then it wouldnt. Every time I unhooked cable at trans. and hooked it back up it would work for awhile then quit. If this sounds the same,let me know, its not that hard to fix,just have to pull the tailshaft off, about a 30 min, job.
Good luck

 

[jz7p6t]

If you have to replace the Speedo Drive Gear/Clip, you will have to remove the Trans Tailshaft Housing (not the Tailshaft) which is attached to the Trans with 4 bolts and attached to the Trans Crossmember with 2 bolts. You will first have to remove the driveshaft which attaches to the rear axle with 2 u-bolts and 4 nuts, as soon as you remove the driveshaft tape over the u-joint bearings to keep them from falling off and losing the rollers. You may also have to remove the crossmember and the exhaust system. If you can put the car on a hoist and have a friend to help, it will go a lot quicker! Good Luck.

 

[Imachad]

My Speedo is about 10 mph off as in 10 over actual speed. - calibrated by those road side stationary cop cars with a speedo reading. Any ideas on why? Tires are spec.

Chad