Speedo problem , changed cable , trans gear and gauge

[jerry6]

used to be the needle would jump from 0 up to 40 mph , then over 50 would settle a bit and only swing 4-8 mph ., now it only jumps until I get up to 8-10 mph then it is steady all the way up
Just wondering what the problem is , rallye gauges ,new speedo rebuilt , new cable and trans gear . Is there a fix for this ?
At least now it does not make noise like before the parts change rebuild , but would like a smooth needle on the speedo if possible .

 

[RedFish]

Something as simple as cable routing can cause noise and/or make the needle jump.
If you pulled the cable end to you to have ample and easy attach at the speedo, pushing a bit of length back through the firewall grommet will relax the turn at the strap under the drivers seat. I've seen that strap hammered down tight too which wouldn't allow the cable sheathe to move.
Assembly line workers would grab it near that strap and push and pull on it seeking the sweet spot but... If you have headers or whatever that change the routing you may not find the sweet spot.
It may still be a fault in the instrument too. Good luck with it.

 

[fishy68]

When you installed the trans. gear did you clock it properly?

 

[wjajr]

When you installed the trans. gear did you clock it properly?

X2. If improperly clocked, spedo gear won’t mesh well with its mate in the tail shaft, causing binding, or poor contact.

 

[jerry6]

I'm pretty sure , but I'll check it out again . Tested my old gauge with new cable and a drill , it still jumps around like crazy , so it's a good thing I replaced it .
Will try re seating the cable , play around with it , hope it helps , I really don't like the needle jumping , even if only for the first 5-10 mph .
Maybe I'm a bit to anal for a classic car ? Funny cause on my new cars I really don't give a damn about things like this .

 

[fishy68]

Dancing speedo's drive me crazy too.

 

[wjajr]

I think I can take a little jump from a vintage speedo a lot better than these goofy video game gages found on new cars. Having speedo and tachometer sweep a complete ark and back to zero at engine start drives me nuts… What’s next a vibrating seat so you know the car is moving; oh yeah, Caddy now has this as an obstruction warning when in moving in reverse.

I suspect that the cable is bent a bit too tightly at some point causing it to momentarily fetch up once moving. Make sure inner cable is fully lubed, and cable has no abrupt bends.