Does your speedometer needle bounce at speed?

[TurboChris]

This has been bugging me forever. My speedometer needle in my 66 Fairlane bounces as much as 10 mph when I'm doing 50-75 on the freeway. The cable was replaced when I swapped in the TKX so I ASSumed it must be the speedo head itself (it also did it with the C6). I removed the cluster and took it into a speedometer shop today and he hooked it up to a tester he has and it was perfectly steady at speeds up past 100.

But

I noticed as he stood there holding my instrument cluster that if he moved slightly it did exhibit some bounce.

What say you all? Does your classic car have much if any bounce at speed?

Video for reference (with the C6 but it's the same with the TKX)
https://youtu.be/OYk7D6QcchY?si=pkiSKUs6VA26G7yk

[frankenfords]

My guess is the cable needs to be lubed. Many companies sell a dry graphite lube in a tube. Pull the cable all the way out of the sheathing, put it back in while applying liberal amounts of the dry graphite, that should solve the problem. If it doesn't, maybe look for kinks or hard bends in the cable and sheathing.

[1964Fastback]

Also I think the inner core will only pull out from the speedometer end, not the transmission end, because of a crimped bead on the top end of the core wire.

Pat

[galaxiex]

Bends in the cable must be large radius and smooth.
No tight bends or kinks.

I've encountered factory cable installations
where using any or some of the factory cable hold down clips,
they put a very mild kink in the cable and cause that kind of bounce.
So mild a kink you would "think" it's ok, but no.

Remove the clip and let the cable find its "natural" position.
Extend the clip somehow to hold the cable in its/that natural position.

This can be tricky if the kink is up under the dash.
Not much room there....

By the same token, a cable that is unsupported and "floating" in space can cause the same issue.
It needs to be restrained, but in natural non kinked way.