Similar situation on my 56 but nowhere near as bad, usually 57 to 67 which implies tires.... Anyhoo, after last test ride (Sat 14) , seems like pavement made a great difference, and said vibration settled down after driving perhaps 15 miles (car had sat 2 weeks) at highway speeds. Tires freshly balanced 2 days earlier. So I said maybe flatspotting? I am not in love with those firestones anyway, but recall a similar vibration when my 87 LeBaron had a bad tire belt. Would not be my u jts since have new driveshaft with sealed modern joints. now--- I recall that when installing all style of U joints the front and rear joints should be out of phase with one another? i.e. each major axis of the cross must not be the same, they should be at 90 deg to each other. If one is parallel with the ground the other should be vertical. Also believe its about 1.5 oz per boot? but dont hold me to this, check your shop or Motors manual. I'd check the phasing of the joints first... then the tires. L. |