Speedometer quit
Thread Starter
Racer
Joined: Nov 2011
Posts: 374
Likes: 21
From: Charleston SC
Speedometer quit
Two minor (I hope) problems cropped up this moring. The speedometer quit working. Every once in a while it acts like it wants to work, needle flips up and down a couple of times, but mostly reads 0 and the odometer moves slightly but mostly doesn't. Other problem is the right turn signal indicator quit. Outside lights, including brake/running/turn signal, work fine. Bulb is good. If ether of these require removing the dash panel, I'm gonna need help. If somebody can write me up step-by-step instructions or direct me to a link, I'd sure appreciate it. Have a great day, brgds, Bill
Melting Slicks
Joined: Mar 2006
Posts: 2,248
Likes: 67
From: Warrington PA
Finalist 2020 C4 of the Year - Unmodified
Most likely you need a new speedo cable, which can be a little involed unless you have small hands to get up under the dash.
Are you saying that the bulb in the dash is out for the RH turn signal? If so, again small hands need or have to do some removal to correct the problem.
Wilcox has excellent tech articles on their web site, with great illustrations, also do a search here in the tech section, there are also excellent threads and posts here to accomplish exactly what you need to do. Hope this helped................................To m
Are you saying that the bulb in the dash is out for the RH turn signal? If so, again small hands need or have to do some removal to correct the problem.
Wilcox has excellent tech articles on their web site, with great illustrations, also do a search here in the tech section, there are also excellent threads and posts here to accomplish exactly what you need to do. Hope this helped................................To m
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
When mine did that I bought a new cable, installed it, and found that it didn't fix the problem. Most likely the plastic driven gear teeth have worn just enough so that they no longer engage with the drive gear.A replacement shouldn't be more than about $10 or so...all the Corvette suppliers sell them.
Thread Starter
Racer
Joined: Nov 2011
Posts: 374
Likes: 21
From: Charleston SC
When mine did that I bought a new cable, installed it, and found that it didn't fix the problem. Most likely the plastic driven gear teeth have worn just enough so that they no longer engage with the drive gear.A replacement shouldn't be more than about $10 or so...all the Corvette suppliers sell them.
Drifting
Joined: Oct 2005
Posts: 1,331
Likes: 479
From: Appleton Wisconsin
Well, it's not the cable. Tried the electric drill test and speedo passed with flying colors. The small plastic gear on the adaptor (90 degree that goes into the trans) looked OK but got another ($7) just to make sure. Not that either. That leaves about one other option: Large gear in the tailshaft! Why the he!! do they make that part out of PLASTIC? I can understand the gear on the adaptor being made out of plastic because it takes about 10 minutes to replace. But plastic inside the transmission??? A 10 minute repair usually takes me a day to complete; this job is probably gonna tie up the car 2-3 months! BTW, if anyone has any other possible causes, please chime in before I dive in. Have a great day, Bill
Thread Starter
Racer
Joined: Nov 2011
Posts: 374
Likes: 21
From: Charleston SC
[QUOTE=Big Block Dave;1582999656]Did you check the adapter to make sure that both ends are turning? How about the little plastic sheath the the cable goes into before it goes into the adapter? cracked, worn?[/QUOTE
The adapter, as far as I can tell, is fine. Everything working like it should. Nothing broken, bent, worn, etc. I don't have the knowledge, equipment, or space to do "dropping driveshafts" kind of repair so I just gotta hope my mechanic won't do too much damage (to my checking account). Y'all have a wonnerful week, Bill
The adapter, as far as I can tell, is fine. Everything working like it should. Nothing broken, bent, worn, etc. I don't have the knowledge, equipment, or space to do "dropping driveshafts" kind of repair so I just gotta hope my mechanic won't do too much damage (to my checking account). Y'all have a wonnerful week, Bill
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Advanced
Joined: Jul 2007
Posts: 72
Likes: 2
I chased a speedometer problem on my son's 74' for almost a year. I pulled the speedometer and had the head rebuilt, replaced the cable, replaced the plastic driven gear - all to no avail. I finally noticed that the small adapter gearbox that is attached to the transmission (4 speed) was a little sloppy - i e not held rigidly in one place. It is only held on by a flat plate which goes into a slot in the side of the adapter and a single bolt into the side of the transmission. I made up a new attachment plate of slightly thicker steel material. That fixed the problem - I assume that the slop was allowing the gears to come out of engagement and when the slop was removed the gears mated properly.
Thread Starter
Racer
Joined: Nov 2011
Posts: 374
Likes: 21
From: Charleston SC
I chased a speedometer problem on my son's 74' for almost a year. I pulled the speedometer and had the head rebuilt, replaced the cable, replaced the plastic driven gear - all to no avail. I finally noticed that the small adapter gearbox that is attached to the transmission (4 speed) was a little sloppy - i e not held rigidly in one place. It is only held on by a flat plate which goes into a slot in the side of the adapter and a single bolt into the side of the transmission. I made up a new attachment plate of slightly thicker steel material. That fixed the problem - I assume that the slop was allowing the gears to come out of engagement and when the slop was removed the gears mated properly.
Thread Starter
Racer
Joined: Nov 2011
Posts: 374
Likes: 21
From: Charleston SC
I chased a speedometer problem on my son's 74' for almost a year. I pulled the speedometer and had the head rebuilt, replaced the cable, replaced the plastic driven gear - all to no avail. I finally noticed that the small adapter gearbox that is attached to the transmission (4 speed) was a little sloppy - i e not held rigidly in one place. It is only held on by a flat plate which goes into a slot in the side of the adapter and a single bolt into the side of the transmission. I made up a new attachment plate of slightly thicker steel material. That fixed the problem - I assume that the slop was allowing the gears to come out of engagement and when the slop was removed the gears mated properly.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Glad you got it fixed. With an auto trans in 74 (I don't recall if it's a TH 400 or 350), either one, $410 is a large chunk of cash to pull the driveshaft and 4 bolts to access it. Even in a Corvette. The Trans does NOT have to be removed, only the tailshaft housing.
Thread Starter
Racer
Joined: Nov 2011
Posts: 374
Likes: 21
From: Charleston SC
I have a 4sp and I agree that it just involves tailshaft removal. I was in the Chevy dealer to pick up the small $7 gear and asked them for an estimate in case it was the large in-trans gear. I would have never paid that much. I would have tried replacing the large gear myself and then had the car towed to my local 'Vette mechanic when I screwed it up! BTW, drove it this morning and it STILL WORKS! Have a great day, Bill
Advanced
Joined: Jul 2007
Posts: 72
Likes: 2
I'm glad that fixing the attachment of the adapter gearbox to the side of the transmission did the trick for you as it did for me. The repair I did to my son's 74' was almost 10 years ago and his speedometer is still working fine so I think you are all set.