Here’s the short of it... i recently purchased an 88 GT with a jumpy speedometer. I replaced the speedometer cable not once, not twice, but yes - three times with the same results. I removed the cluster and checked the speedometer mechanism & do not see anything evident with it (moves freely with no excessive play). Stretched the cable out straight and rotated it with a drill — still jumpy. Anyone experience this??? SOOOOO tired of pulling the cluster.