rear end vibration

[strad]

I'm still having vibration in the rear end of my 72 Duster. I have re-balanced the drive shaft, checked all the bearings (pinion/wheel)changed the third member, tires are balanced etc. and shimed the springs to be within the 4-5 degree tolerance. However, when we did the shimming it changed where the vibration started ( it used to start around 50mph, now it is around 60 and has a lower rumble around 15 mph, although not quite as pronounced as before the re-shimming) I am at a total loss to figure this out, the only thing that I have noticed is that the springs are a little saggy ( when I have three fat boys in the car the wheel rubs on the body) could this be it, or something else.
Any help is appreciated

 

[player1up]

I'll take a stab at this. Could very well be the rear springs and/or the shocks. The springs not being as stiff as they once were along with the body not being as stiff as it was 35 years ago either. Sub-frame connectors and new leaf springs should be on the list but not first on the list.

Is this a buzzing ( high speed sounding ) or a woob woob woob ( low speed sounding ) thing. Based on the shimming changing the speed at which it occurs could mean that you're on the right track....did you check the axle bearings... remember reading that it is a common thing to cause strange vibrations.

 

[RedFish]

Replace U joints.