Joined: Sun Jul 13 2014, 10:04PM
Location: Mechanicsburg , PA
Posts: 151
I've noticed that my speedometer jumps around once I get it above 50mph. Does the cable need replaced or is it something else? If it does need replaced, where can I find one?
Joined: Sat Oct 15 2005, 04:54AM
Location: Spokane,Wa.
Posts: 170
If its kinked a replacement is probably in order, Junk yard is where I would go. However, my experience is that it is dry and dirty. Reach up under the dash and disconnect the cable from the back of the housing(threaded). Pull the tip of the cable down so you can see it. Slide/pull the inner steel cable out of the housing(appx 4-5ft long). Clean and lube it with some light grease, all up and down the cable. Reinstall and see if the bounce is gone.. Always has worked for my fleet.
Joined: Sun Jan 07 2007, 07:37PM
Location: London,Ontario
Posts: 166
I you get to 50mph before this occurs, the first thing I would recommend is to inspect the drive gear at the tranny. If you remove it, put witness marks on the housing as some are adjustable and have index marks on the exterior. If the gear shows signs of centre wear, replace it before moving on. You can completely remove the drive cable, clean it with brake clean, dry it thoroughly and reinstall using dry graphite lube only which comes in a tube. Be aware that the sheath itself may be worn on the inside ( especially on the inside of the curves ) and no lube in the world will stay on the cable as it justs scuffs off. You really have "metal to metal" at any inside bend in the sheath. Probabilities are that an entire cable may be needed just make sure to measure the length and match the ends with your old one. There are other factors that can cause needles to bounce and the main one is the register mechanism mounted on the rear of the speedo but cleaning and lubing requires removal of the head. With a #2 Robertson driver chucked up in a cordless variable speed drill you can mimic the drive cable's effect on the speedo head by engaging the driver bit in the square of the speedometer and slowly increasing the speed of the drill. I'm pretty sure the relationship between the inner and outer spinning parts of the speed mechanism is based on magnetic attraction rather than friction. While spinning the drive mechanism of the speedo you can lightly spray the moving parts and bushings with WD40 being careful not to over spray and get it on the mileage register wheels or dash face. A toothpick can be used which has been dipped in the cleaner. I hope this information helps as it is what I did to get rid of my "needle bounce" - that was two years ago and the speedo has been smoth and even since. Oh, one more thing you can try - Keep it under 50!
Joined: Sun Jan 07 2007, 07:37PM
Location: London,Ontario
Posts: 166
The smoother the cable rotation ( without pulsing or surging ) the less the speedometer needle will waiver. If movement of the needle is steady driven by a cordless drill ( which does not pulse when turning ) then you'd have to conclude the issue is with the driven input to the speedo head, that being cable and drive gear . You can actually spin the cable where it connects to the tranny itself using the above method by connecting a variable speed drill to the end of the cable where it connects to the drive gear. This is a bit like solving an electrical issue where you work your way backwards until you find the real source of an issue.
Joined: Sat Oct 15 2005, 04:54AM
Location: Spokane,Wa.
Posts: 170
You can lube it in 20 minutes start to finish. Then drive it and see. Why spend 5 hours diagnosing a dry cable? Out of 6 mopars with bouncing needles, all were fixed with a lil lube.. Your call though..
Joined: Fri May 22 2009, 04:03PM
Location: richmond hill, ontario
Posts: 106
My 66 does the same thing periodically. I took out and lubed the cable and it didn't help. so I took out speedo cluster and unscrewed cover and lightly lubed the spinning parts inside with wd40 with the tube on to be exact. worked like a charm.