I was wondering if anyone could give me some advise. I have a 1955 F-100 with a 1979 302 / C6 in it. I am having isues with my speedometer not working correctly. It continually jumps around as I am driving and makes a squieling noise. I have replaces the cable, the worm gear and the speedometer with another origional one that I have but the problem contiues. This is not a new issue as I had the same problem when the truck had a 272 / 4 speed in it. I am now thinking that it might be possible that both guages I have tried are bad, however before I spend the moey to have them rebuilt i want to make sureI am not over looking something.