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Speedometer needle jumping

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davidk

davidk

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I have recently installed a TRF speedometer cable. The needle is jumping, especially at low speeds. It didn't do this before the new cable was installed. I think the cable needs to be lubricated. I've read past posts on the subject, but I don't recall what lubricant should be used. Any suggestions? Any other possible causes? Thanks for the help! David K.
 
I think it is more likely the cable is not installed tightly in one of the ends. Try to reinstall each again. I think this was a problem in the past.
 
I had the same problem w/ a TRF tach cable; I had flipped the ends of the cable....
 
check the recommended cable length going into the speedo. On the TR4, I think it is 3/8" (can't remember if that is in the manual, or web info, or I just made it up). My replacement cable was too long and needed to be ground down a bit. You may have the same issue.

Randy
 
Ditto here with my new TRF speedo cable.
I took it out and made sure both drive ends were
well seated before I tightened down the fastener
threads.

Jumping around cured!

d
 
tdskip said:
davidk said:
I think the cable needs to be lubricated.
Click to expand...

The TR8 speedometer did this and I ignored it, and the cable snapped from a lack of lubriction. Doh!
Click to expand...

My 8 does the same thing,only at freeway speeds.
So where is the guide to lubing the cable?
 
... and make sure there are no tight bends in the cable.
 
For lubricating:
I have used WD-40 with success but read that graphite is better.
 
IMO, MoS2 (molybdenum disulphide or moly for short) is even better than graphite. Either liquid or powder will work fine, but powder is somewhat less messy to apply (and less expensive). Take the center cable out and rub the powder (or spray the liquid) directly onto the length of the core, then reinsert it in the outer housing.
 
In high school auto shop we used to lube speedo cables with lithium grease. Later at an MG club tech session, the mechanic holding the session mentioned that he used to get special Ford speedometer lube which was, I think (forgive the fading memory from 20 years ago), made mostly of molybdenum disulphide. Since my Midget was the guinea pig for the tech session, it got both its speedo and tach cables lubed with the stuff, and those needles were rock steady for the remaining two years that I owned the car.

Scott
 
David, I hope your satisfied I tried to hook up the speedo end of the cable today and noticed my brand new but not recent purchased cabled end was all buggered up.I find you responsible some how! /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
All you out there if I replace the inside can I leave the trans end in?
 
My replacement cable from TRF did not work when I put it in. Comparing it to the broken one that used to work, I saw that the speedo cable end was a little shorter to the plastic tab. After asking TRF about it, then checking the spec, and us verifying that the one they sent was correct, it started working. Hasn't stopped. But this past week, it started bouncing at about 20mph.

I'm going to try that lube when I get a chance, but I'm sort of afraid to break it. I took it out and replaced it 3 or 5 times, and it didn't start working until I filled up at a gas station -basically unexplained.

I think the old one was from VB, and they have a litle more cable between the plastic tab and the end that inserts into the speedo.

Jer
 
They didn't know what "MoS2 (molybdenum disulphide or moly for short)" was at the parts store. I have some white lithium in a spray can, and some "Engine Assembly Lube with Moly-ghraphite" which is better for the speedometer cable?
 
Try asking for "Dri Slide" at the local gun shop.

Given only the choice of white lithium or engine assembly lube; I'd go for the white lithium. Assembly lube is not optimized for long life.

Sounds to me like your cable is not protruding far enough at one end or the other, and finally just barely caught. You might be able to solve the problem by determining which end is short, and sliding the inner cable through the plastic retaining collar at the speedo head end to compensate. If you take the speedo end loose and can turn the inner cable in your fingers, it needs to go towards the transmission (which is apparently a common problem from what I've heard). If the head end is short, then the speedo/odo won't move when you take the gearbox end loose and turn the cable with your fingers.

PS, McMaster-Carr has a wide variety of 'moly' lubricants, and their service is downright sudden. If you order right now, you might get it by tomorrow afternoon.
https://www.mcmaster.com/
 
My tach and speedo had the same problem and it had nothing to do with the cable! I think this is a common mistake to assume the problem is in the cable when it is actually in the tach or speedo itself.

With that said, replacing the cable is inexpensive to try when trouble shooting but don't overlook the instruments, they do seize up!
 
/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif
The instruments can even be the cause of broken cables. When my latest Stag came to me, the PO had just replaced the speedo cable & angle drive and driven around the block to check that the speedo worked. I was less than 30 miles down the road before the angle drive broke again ... the speedo head would turn when cool, but bind tightly once it got hot.
 
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