1969 f40 speedometer going bonkers??? (1 Viewer)

[sheepdawg]

Suddenly my speedometer needle will oscilate back and forth sometimes up to 40 mph range throughout my acceleration. For example, when I am traveling 60 mph, my needle oscillates between 40 mph and 80 mph. This will go on initially and after about 15 minutes of driving, it stops and then will read the proper speed. It is beginning to occur more frequently and I do not know what the cause is. I have checked the speedometer cable and it looks to be in good shape.

I searched the forum and did not see anything addressing this, does anyone have any idea why it is doing this and what can I do to stop the issue?

Any suggestion would be greatly appreciated.

 

[sggoat]

Seems maybe it's getting "stuck" in the sheath and may be binding a little, until it gets hot, then letting go--might try a lot of Kroil down the shaft to see if this helps.(squirt it in the cable from the gauge cluster end)

 

[Brownd3max]

After squirting liberal amounts of penetrating oil (I like Liquid Wrench Penetrating oil) like sggoat said, I would take a real close look at the speedo ass'y in the dash. Maybe the the rotating "whirlygig" at the cable's end is hitting the stationary cup it spins in. my .02...

 

[sheepdawg]

Tried using Kroil with no success. Time for a new speedo cable.

 

[Brownd3max]

I'm still curious how a speedo cable can get "stuck" without breaking something attached to it at one end or the other. I look forward to you reporting what you find when you get the old one out. Good luck!

 

[ferg]

Had same problem way back when. Problem was bad cable, even though I could not see anything wrong with it.

 

[Brownd3max]

Interesting- maybe it's "notching" momentarily while rotating, like the second hand of an old analog wall clock, only faster of course!

 

[Speeter]

I had the exact same problem. Then the speedo went to about 2x actual speed and then it died. Had it fixed by Bobs speedometers. Great service but very spendy. I would definitely change out the cable to be sure it is not the issue or causing more damage. Cheap insurance and test. Good luck.