Speedometer needle jumps around

Sprucegum

Bigger Hammer
Dec 9, 2016
35
Vermont
First Name
Dave
Willys Model
  1. CJ
Willys Year:
  1. 1957
Finally got my project purring like a kitten or maybe like a tomcat as the exhaust still needs work. Took it for a little no registration cruse down the gravel road that I live on to get a feel for other issues. I had no idea if the speedometer worked so I kept a eye on it and the needle does move and looks to be ballpark accurate but it really jumps around a lot, sort of goes into a flutter around what I am guessing is the more or less accurate speed. I only got it up around 20 as it has no back brakes. Having never owned a jeep before I don't know if the fluttering needle is kind of a old jeep thing or if I should be looking for a problem. Really happy with my project so far when I purchased it last fall it would barely go up the trailer ramps in low range, former owner said he had tried everything to make it run better and seemed pretty discouraged. A good fuel system cleaning, carb rebuild, and wait for it--------------------------putting the plug wires on the correct plugs seemed to cure everything.
 
In my experience with older AMC cars, the fluttering speedometer is due to either a binding speedometer cable, or an old speedometer. The things worked by spinning a magnet inside a metal housing. The magnet was spun by the cable and the housing was moved by the magnetic pull of the spinning magnet. The metal housing would then move the needle. Rust on the assembly can cause intermittent and inaccurate needle movement. WD-40 the back of the speedometer and see if that helps.

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At the top of the gauge housing where the cable goes in, is an oil port. You are supposed to put a couple drops of oil in it like once a year or something. I seriously doubt the part of scheduled maintenance was done regularly, if ever, on most of these. I would not use WD40 as that is NOT a lubricant, but a cleaner. And it may very well make a bigger mess inside being very light. I'd suggest you do what the manufacturer suggested and drop couple drops of oil in the little brass cup. It's at the top so unless you either remove it, or unbolt the dash and it will pivot down just enough to see what you are doing. A pain in the posterior, hence why it was not done much.
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Good to know, I will be starting a rewire job soon so oiling the old speedo at the same time will not be much bother. Makes me think of the oil hole in the fan bearing of the old Farmall tractors that was supposed to be filled with oil, no one ever did it untill it was too late.
 
You can completely remove the speedo cable and put it on the bench.
Then you can remove the square, inner "wire" from the "coil spring" housing.
Clean it all up, lube it and put it all back.
That should fix it for another 50 years.
If that doesn't fix it, then it's the speedo itself.
 
I have a 63 jeep 4wd truck. Last couple of years applying the brake and clutch at the same time seems to effect my braking. Anyone heard of that? Only good side to it is if anyone stole the truck they'd probably crash it because you have to apply brakes alone or seems to be interference.
 
OOPS I meant to say I fixed that speedo problem just by soaking the entire cable and metal cover in liquid graphite
 
JeepBebop said:
I have a 63 jeep 4wd truck. Last couple of years applying the brake and clutch at the same time seems to effect my braking. Anyone heard of that?
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First thing I'd check is if the two pedals are somehow interfering with each other on the pivot shaft under the floor. Both pedals rotate on the same shaft. Go under with a bright light and have someone push the pedals up and down slowly so you can watch what's happening.
 
I have two 1946 CJ2A's. One has an old speedometer and the other has a new one. The new speedometer jumps around where as the old one is steady as a rock. It maybe the problem is with the unit being an import.
 
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