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The speedometer on my XJ had the 'jumping needle' syndrome where the needle would twitch or jump around. I accidently came across the fix this past weekend. Two items.
First, I pulled the cable off the front axle drive. I poked a small allen wrench into the drive unit, and found that at first it would only go in a short distance. A gentle push and it went further. So, I ran the wrench back and forth a few times, then lubricated the end of the cable with white lithium grease and put it back on. My theory is that the cable end needs to slide back and forth a bit as the forks compress and extend going over bumps. With the passage blocked the cable couldn't move as it should. Just for good measure I did the same bit at the speedo end.
This helped, but did not eliminate the problem. I figured it was just the old speedo's way of working. Then I took off the tank as part of a valve cover gasket replacement job. Guess what...the speedo cable was routed incorrectly. It had a wear spot on the outer housing where it had been rubbing the frame. Cable had been routed behind the lower tripple-T, then in front of the upper tripple-T before connecting to the speedo. I took off the cable at the speedo end, routed it in front of both tripple-T supports, and re-connected it to the speedo. Needle no longer bounces.
Moral of this story...if your speedometer needle is bouncing, check the cable routing.
First, I pulled the cable off the front axle drive. I poked a small allen wrench into the drive unit, and found that at first it would only go in a short distance. A gentle push and it went further. So, I ran the wrench back and forth a few times, then lubricated the end of the cable with white lithium grease and put it back on. My theory is that the cable end needs to slide back and forth a bit as the forks compress and extend going over bumps. With the passage blocked the cable couldn't move as it should. Just for good measure I did the same bit at the speedo end.
This helped, but did not eliminate the problem. I figured it was just the old speedo's way of working. Then I took off the tank as part of a valve cover gasket replacement job. Guess what...the speedo cable was routed incorrectly. It had a wear spot on the outer housing where it had been rubbing the frame. Cable had been routed behind the lower tripple-T, then in front of the upper tripple-T before connecting to the speedo. I took off the cable at the speedo end, routed it in front of both tripple-T supports, and re-connected it to the speedo. Needle no longer bounces.
Moral of this story...if your speedometer needle is bouncing, check the cable routing.
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