A904 with the black gear. Cable turns freely when out of the car, but when under 35mph it jumps up and down. After that it smooths out. Any ideas what it is and how to fix it?

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'66 Barracuda super six turbo??

The first thing to try is lubing the cable. Unscrew or unclip the cable housing from the speedo head, push it forward towards the front of the car, then pull it down below the dash. Pull the cable itself out of the housing (be careful, it'll probably have gunk on it, and you don't want to stain your seats/carpet/clothes.)

Clean the entire length of the cable by wiping it down with carburetor cleaner or denatured alcohol. Inspect its whole length for fraying or damage.

Get some white lithium grease and put a spoonful of it into a small bowl (I use an aerosol spray cap). Puff a goodly amount of powdered graphite onto the grease. Mix it in until the grease is a uniform shiny black. Back at the car, place a glob of the grease on your hand, between the first and second fingers. Holding these two fingers loosely but closely together, push the cable through the grease, through your fingers and into the housing. The idea is to get some grease on the cable, but avoid big blobs or slops. Once there's only about 9" of cable left to push in, stop, clean all the grease off your hands and the glob off the cable, then push the cable the rest of the way in. You may have to pull back slightly, rotate the cable a fraction of a turn, and then push forward again to line up the transmission end of the cable with its nylon drive pinion. Once this is done, reinstall the cable on the speedo head and try it out. If this solves the waving needle, you're pretty much all set.

Assuming the cable has been carefully checked for damage and lubricated and the problem still occurs, the bearing is shot in your speedometer, letting the driven cup sag down to the point where it physically hits the stirrup and makes the needle bounce. There's sometimes a tiny little cup plug above the bearing, with an even tinier hole in it, to let you oil the bearing, but nobody in the history of ever has had that on their periodic-maintenance list, so too late now. Pull the speedo head and send it to:

DeLuxe Speedometer & Cable
2330 S Kalamath St. Ste A
Denver, CO 80223
Toll free 888-907-6505

for rebuild-and-return service.

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