Hello Wise Ones,
I will try make this quick and to the point. I have a 95 F150 and it has a 5 or 6" Lift. The whole time Ive had the truck is has had the lift and this vibration. It Vibrates when you left off the gas, but only at speeds above 80Km/h. Drives smooth anything below 80. The Faster the you the worse it gets, and I would say doing about 100 km/h you notice the vibration all the time (not only when coasting).

I have checked and changed every U joint of the Rear Driveshaft, and it seemed to help slightly, but certaintly did not fix the issue.
That is where my knowledge and experience stops, and I am looking for advice, or links to other threads on this topic.

I suspect the lift could have something to do with it and the diff. The rear diff is just spaced up with blocks. I assume the Pinion angle would not change if the front and back was lifted the same, so I dont think that is it.

I dont really know how to check the diff angle, so if anyone is willing to chime in I am willing to try it. I rotating the yoke when I had the shaft off (if I am talking about the right thing) from the diff, and it moves about 1/4" turn, which I believe is normal.

This is my first post here, so thank you, and looking forward to some brilliant responses.

 

Have you had the tires balanced?

 

Yeah tires are good. Does it with the old summers, and same with the new winters.
Thanks for the suggestion