mr_stoop

I see there have been a few posts in this forum regarding the unknown vibration. I haven't found one, however, that contains similar symptoms to the vibration that I am experiencing. Hopefully you guys can help me out.

The first thing that I did after reading some threads was change the tail shaft bushing after noticing that the drive shaft had significant play (1/8" or so). This may have reduced some of the vibration, but certainly not the better part of it. I have also jacked the tires off the ground to check for play, drivers rear has little play, tire barely moves when twisted back and forth, passenger rear has no play, but both the front tires have significant play.

The vibration's symptoms/characteristics are as follows:
- become noticeable at 60mph and greater
- increases in magnitude up to about 75mph and then maintains a steady state
- is worse during acceleration
- is less during deceleration
- felt in the rear as well as in the steering wheel
- is not felt at all when in neutral above 60 mph

What should I try next? What do you guys think?

MelWff

based on your description could be multiple causes. Starting with the front you are not to clear how you tested for play. So you could have worn ball joints, tie rod ends, idler arm, etc. Get those items checked as well as having all wheels balanced.
In the rear, is the play is the wheel bearing or is the halft shaft yoke moving in and out of the rear?

cv67

Check your pinion bearing to see if it has any noticeable slop in it.
Sometimes it only takes a small measureable amount to give an issue