Speedometer Needle Bouncing

[DT1]

So, I'm working out the last of the bugs after restoring the 72. The last item is the speedometer. I noticed on the test ride a ticking sound. Sort of like a pebble was stuck in the tire tread. Then I noticed the speedometer needle was bouncing quite a bit. This has happened with other vehicles I've had and the fix is to either lube the cable or replace it. I figured that the cable was one of the only parts I didn't replace so I ordered a new cable from Summit Racing. When I got it, I was surprised at the cable length. My original cable was 62 inches long and this new one from Summit is 120 inches long. Really? What kind of vehicle takes a 120 inch cable? This is the only cable that Summit has for my application so I figured I'd creatively route it, being careful not to make any sharp turns to avoid any kinks. I also pre-lubed it before I installed it. After it was all finished, I took the truck on the road. No change at all. Still ticking and bouncing. What else but the cable would cause this?