Speedometer problems

[T.R.]

The speedometer needle was not steady, so I replaced the speedometer cable and speedometer and it is still not steady. What should I look for next. Has anyone had this problem before and what might be the fix.
Thanks for any and all help.

[Lifer]

A couple of things come to mind. There could still be some crud in the cable housing which is causing it to bind a little. The cable and its housing could be kinked or pinched somewhere. They could also be routed incorrectly, causing too tight a bend in the cable. (That pretty much identifies all possible problems with the cable, all of which are easy fixes.)

Another possibility, once you're sure that the cable is good to go, is that the magnets that pull the speedo needle up could be weak. Checking this out and fixing it is not something the average "shade tree" mechanic would be able to handle, but a speedo shop would be able to rebuild it in nothing flat.

[MSeriesRebuild]

The speedometer needle was not steady, so I replaced the speedometer cable and speedometer and it is still not steady. What should I look for next. Has anyone had this problem before and what might be the fix.
Thanks for any and all help.

If you have already replaced your drive cable with new or known good cable that is well lubed and routed correctly without sharp bends as Lifer mentioned, you may as well go for a speedo head. Buying a new one is likely cheaper than a total rebuild, but you could check with an instrument repair shop in your area if you have a local one. We have new units for $63.75 + shipping.

[cuz]

When you say new speedo cable do you mean the inner flex cable only or the inner flex cable with a new outer housing as well?

Worn outer housings will allow a new inner cable to vibrate and flex causing the needle float.

To check the speedo itself just remove it and chuck an old cable end or a small nail in an electric drill and run the drill in reverse with the nail or cable end inserted GENTLY into the head. If the needle still floats or bounces at a steady drill RPM then you know it's the speedo head.

[HingsingM37]

I seem to remember that like vintage aircraft, if you have a older speedo you will have radium paint on the needle and face. I wouldn't attempt to tear into that, better to replace than to take apart if you were thinking of tinkering with it to save $. . If I recall an easy way to tell is to keep the speedometer or gauge away from light then look at it in darkness and see if it glows on it's own without exposure to light, most likely radium, Another test is to point a flashlight at it then turn it off. If the display drastically brightens its phosphorus paint and you are ok. If it does not charge up with the flashlight and keeps the same eerie green glow, it is radium and is most toxic. The guys here will correct me on this if I am incorrect. It may be a non-issue but that is what I recall?

[cuz]

There are hundreds of articles and opinions on exposure to instruments containing radium painted lettering and numerals. They run the full gamut from no worries at all to you'll die within 5 minutes.

Anyone who wants to learn more about the topic should read a few of these articles and using your own head make your own decision.

They are not a problem on the handful of exposures normally encountered in your day to day life around these vehicles and old aircraft. The Naders have set off huge alarms and as usual the loudest voice is the voice most folks hear. Instrument shops have refused to work on them for years. Not because one exposure can kill them. Because the volume they deal with can be hazardous and is also a disposal problem.

[M-Thrax]

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[T.R.]

The speedometer needle was not steady, so I replaced the speedometer cable and speedometer and it is still not steady. What should I look for next. Has anyone had this problem before and what might be the fix.
Thanks for any and all help.

Additional information:

The speedometer cable and housing are new and appear to be well greased, the cable has no sharp bends.

I replaced the first speedometer with a speedometer that is known to be good and it is doing the exact same thing the first speedometer was doing.

My thought was could there be a problem in the transfercase where the speedometer cable attaches. Could something be worn out in the transfercase?

[MSeriesRebuild]

The speedometer needle was not steady, so I replaced the speedometer cable and speedometer and it is still not steady. What should I look for next. Has anyone had this problem before and what might be the fix.
Thanks for any and all help.

Additional information:

The speedometer cable and housing are new and appear to be well greased, the cable has no sharp bends.

I replaced the first speedometer with a speedometer that is known to be good and it is doing the exact same thing the first speedometer was doing.

My thought was could there be a problem in the transfercase where the speedometer cable attaches. Could something be worn out in the transfercase?

Is the grease on the cable core wire of the correct type? Grease that is too stiff will cause this issue also, especially in cold weather. I would suggest you pull out the core wire, clean, and coat it lightly with white lithium grease, reinstall and see if that helps the cause.

The drive gear in the transfer case is heavy duty, very seldom does it cause issues, but you know the story, anything is possible.

[T.R.]

The complete speedometer cable came from Midwest Military, it looks like it is coated with silicone grease would this cause any problem.

[powerwagontim]

Any chance your "silicone grease" is really cosmolene? Cosmolene dosent have very good lubricating properties!
Tim

[MSeriesRebuild]

I would pull the core wire out, clean it, and lube it like I described in my earlier post. Impossible for me to say whether what is in it may cause issues since I have no idea what may be in it. It would also be a good idea to disconnect both ends and spray some aerosol brake cleaner into the cable housing followed by blowing it out good with compressed air. This should rid it of possibly stiff lubricant that could be causing your issue. If doing this doesn't help your cause, I still tend to think the issue is in the speedo head.

[T.R.]

My problem was when I attached the speedometer cable to the transfercase the flexable shaft had a C-clip to keep the shaft from falling out in shipping, the shaft did not engage in the transfercase drive and the shaft pushed against the C-clip which kept it from turning freely.
I also removed the flexable shaft and sprayed it with Lithium grease to be sure it was well lubed.
Took the truck out for a drive around the block and the speedometer was working great.
Thanks for all the input!

[powerwagontim]

Glad you got it figured out!
Tim