Speedometer Issues

Hi All,

I have a 1950 CJ3A I am restoring, the chassis is almost finish. I was hoping someone could help me with a speedometer issue I am having which has me completely stumped. The Speedometer cable comes out of the Dana 18 Transfer case and spins (with the speedometer side of the cable open) at maybe around 100 rpm while the engine is idling and the transmission in first gear. (This rpm speed is a a pure guess as I dont know anyway to accurately read it) The old speedometer was totally trashed so I ordered a new one, when I installed the new speedometer it did nothing. When I put a drill on the speedometer the speedometer did work and the needle moved. I was sure there was a way to calibrate it, so I took it apart and found there is no way to calibrate it.

So the question is... is the problem in the speedometer wanting to many rpms to work or is the problem in the speedometer cable isn't spinning fast enough. Does anyone have any idea how fast the speedometer cable is suppose to spin? I am sure the gear is correct in the transfer case but something isn't right....

Any ideas would be greatly appreciated....

Ardan

 

Again a mystery but you will soon find the solutyion, it seems that it happens when installing a new one. I didn't have this problem.

Whatever, I prefer to look at the road.

 

Sounds like the mechanics are working at both ends.

Are you sure the inner drive cable is long enough, and actually engaging at the speedo when the nut is screwed all the way on? The square tip isn't rounded off?

 

^ this, I can spin my speedo with a twist of my fingers and get a bump of the needle...sounds like the cable is not engaging

 

I was also thinking it wasn't engaging so I took the speedometer apart and hooked it up, the little "flywheel" on the speedometer is spinning when the jeep is running and in first gear just not fast enough to move the needle. If I spin the speedo with my finger I cannot get the needle to move at all.

 

the "flywheel" is called a speed cup, if its turning and the needle isn't moving then something is wrong in the speedo head...or spinning the wrong way??? doesn't seem likely...just throwing it out there

 

x2

 

you say you ordered a new speedo...new to you, brand new repop, brand new OEM?

 

The speedo is direction sensitive so will work one direction only. The speed cup assy works by magnetic induction so it has to spin up pretty good to move the needle. No adjustment avail in speedo. Calibration is done by gear change at transfer case.

 

Maybe, but I think you'd be seeing the needle kick if twisted at "finger speed." And he did get action when using a drill.

 

Thanks for all the good information, One of the things I did check was the direction of turn and it was correct. It is new speedometer, it looks OEM but I am sure it isn't. It just seems it wants to speedo cable to spin faster to make it work. The speedo cable gear in the transfer case is the original and seems to be working.

Maybe I should just buy another speedometer and hope it works...

 

With the cable removed from back of speedo and the transfer case spinning the speedo core, try to pinch the spinning core between your fingers to see if you can stop the core from spinning. The core (squared) portion in transfer case may be rounded off and may be slipping. Pete's right that you should be able to make the needle bounce by spinning it with your fingers.

 

The inner cores are very sensitive to being exactly the right length, and having good tips at each end. Especially if the outer casing may be sketchy from age. Possibly PO may have not crimped the DIY end fitting on tight enough, and it is slipping.

A generic replacement cable "core" kit is easy and cheap. Just needs careful (accurate) fitting.

 

This sounds like a good possibility...how far out the cable casing does the tip if the core extend? the casing might have been stretched out swallowing more core than it should

 

May 3/4 of an inch, I think I will be ordering a new speedometer and cable. I will post the results whenever they come in.

Thanks for all of the feedback....

 

Hi All, the issue was the first "New Speedometer". I ordered another speedometer and it worked just fine out of the box. This has been an issue throughout this rebuilt, so many times parts that are suppose to fit don't, it is so frustrating. Anyway I am glad to have this issue solved, thanks for all of your help...

 

Glad you have things working.