[camaroguy62]

I have a 68 Z-28 that has a driveline vibration between about 55-70 MPH. It occurs in any gear or coasting in neutral, so I don't believe it is engine related. I had a second set of tires and wheels that I changed out on the rear and it still does it. It seems to come from the rear and is severe enough that it rattles the cardboard package shelf. There is no vibration in the steering wheel, some vibration on the shifter, and when I re-bought the car it had this condition. In detailing it, I replaced the following: Front and rear springs, all suspension bushings, body mounts, brake lines and cables, motor and transmission mounts, complete exhaust system--I can't remember if I changed out the universals, but think I did. I had the differential open for inspection-no obvious evidence of problems-replaced the seals. I did not change out the rear wheel bearings, the axles seemed tight in the bearings. I did nothing to the 4 speed close ratio (it's not a rock crusher). I am thinking it must be: driveshaft or universals, transmission output shaft, wheel bearings or axle(s), or pinion angle to transmission angle misalignment. Any help in diagnosing this condition is greatly appreciated. Note: This is a true Z-28, I bought it new, sold it and bought it back. It is mostly numbers matching. The unibody is stiff-no rust or flex.
Camaroguy62