Bouncing speedometer needle

[Stephen717]

Ok so whenever I have the gauges hooked up the tach and speedometer needles bounce. The tach was a N.O.S. sunpro super tach ii that my father had laying around and I'm guessing it's a bad ground issue. The speedometer on the other hand I'm not sure whether it's a cable issue or a gear issue. I just know it bounces constantly. Haven't been able to take it out lately as I've been busy with work but would anyone know if it's the cable needing to be lubed or if it's a bad speedo gear going from the trans to the speedometer cable and what size it'd be if I had to replace it. It's a Saginaw three speed and I'm pretty sure it's never been rebuilt

[HIGHWAY BY THE SEA]

When my speedometer needle kept jumping around it turned out to be a lubrication issue for the cable.

[Astro-Balls]

Put a new cable in, yours is kinked.

[Steeveedee]

Did it do it before you reconnected the cable? It could be as simple as the cable isn't all the way on the speedo. When we got my FiL's truck, the speedo was noisy. All it took was lining the cable up in the speedo head and getting the nut on all the way.

[Stocker]

Could be a lubrication issue -- if so, I used white lithium grease decades ago and not had any problems. I have heard there's something better but I can't recall what.

['68OrangeSunshine]

Graphite powder. Sometimes sold as lock lube.
Doesn't congeal like white lithium.
To be honest, I just look at the GPS on the freeway.

[HO455]

I had the same problem after I moved the cable about 1/2" for my new front shock mounts. Bouncing needle and noisy. I sprayed some white grease in the speedometer end and it slowly got better over about fifty miles and has not been an issue since.
I assume it was because the cable had taken a set after 48 years in the same spot and like everyone does it started complaining when things changed.

[Stocker]

I thought I remembered something about using graphite -- searched & found this by Leon:

Originally Posted by LockDoc

If graphite gets wet it turns into a thick gummy mess. I wouldn't use it....

LockDoc

[toolboxchev]

I have the same problem about once a year. Unscrew cable at both ends, Undo 1 or 2 bolts under the hood and the entire unit should come out.

I cleaned out the both the cable housing and cable with WD 40, sprayed a generous amount into the housing. Cleaned again than relube with some type of light grease or oil of your choosing.

Works like a charm. Dirt is your enemy here.

['68OrangeSunshine]

Originally Posted by Stocker

I thought I remembered something about using graphite -- searched & found this by Leon:

Sure. Depends on climate. I live in Arizona. It's either Dry or Very Dry here. Graphite inside the speedo cable casing -- secured on both ends -- works great.

I once thought white lithium spray grease was the neatest thing since sliced bread. I rebuilt a distributor's weights and springs and really dosed it good with the stuff. In under a year it ''clabbered up'' and gummed up my advance weights. I still use it on door hinges for instance, but I'm leary of using the stuff everywhere.

[toolboxchev]

Yes white lithium is a dirt attractant. More uses in the boating industry, Salt water applications

[John H.]

If it only bounces at lower speeds it usually is the cable. If at all speeds, it is more than likely in the speedo cup or the head unit on speedo. I have had them bounce and had them professionally cleaned out and recalibrated with success.

['68OrangeSunshine]

My speedo works OK up to about 45 - 50. At freeway speeds 65 - 80, the needle bounces between both those numbers. If it's mounted in the cab, I use the GPS for accuracy and ignore the speedo on the freeway.
It's the original instrument from 1968, and has clocked over 390 K.