Hi guys, I picked up a new project; 1975 corvette stingray. It has a few issues to fix, one of which is the speedometer. When driving below 50km/h, the needle “bounces” up and down quite substantially, so you basically don’t know the speed you’re going at. That said, once you go above 50km/h or so, the needle stabilizes and displays the correct speed. Has anyone dealt with this before? Any ideas? Anything is appreciated, thanks!
C3 speedometer needle bounces
- Thread starter charlesorosz
- Start date
Hi Charles,
I had the same issue as you before I swapped in my 6 speed. It could be a number of things. It could be the speedometer gear in the transmission, it could be a sticky speedometer cable which would require you to remove the cable and spray some brake cleaner down it while spinning the sable to get rid of the gunk that is in there. Then spray it with some WD40 or white grease. Or if your car has factory speed control it could be an issue inside that module.
Hopefully this helps. I know after I cleaned inside my cables they were steady from around 10-20kms up. Anything below that was barely bouncing.
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Likely as Jr. Corvette mentioned, it is a sticky cable. That would be my first try. Remove the cable and clean and lubricate as recommended. The tachometer mechanical drive cable can also exhibit the same symptoms.
I’m betting it’s the cables too. Back in the day when all speedos and some tachs were cable driven on just about every car, sticky or broken cables were a common problem. Generally from a lack of lubricant or dried up sticky lube. That’s where I would look first.
Does the dash need to come out to do this?
Yes, the dash does need to be dissassembled to gain access to the speedo and tachometer cables on the rear of the gauges. I suggest if you do decide to dive into this project, clean and lube both the speedo and tachometer cables while you have the dash dissassembled. Also a good time to check all gauge backlamps and vacuum lines while apart, as you do not want to do this job twice.
Does the dash need to come out to do this?
It is possible you could get it with the dash in but it's very tight. If you remove the vent the goes under the steering wheel you may be able to reach up and unhook the speedo cable. It only has a spring tab holding it in so if you press that spring tap down then the cable just pulls out (if it's like my 77). You'll likely have to pull the dash like Ziggy said.
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