Vibration and tailpiece question

[BasscattinBlazer]

Hello to all, This is my very first post on this forum and glad to have a place where can talk to fellow Blazer owners. I have an 85 K5 w 6" lift that has a vibration at low speeds. I just recently had the rear pinion bearing and the u-joints replaced but the vibration still exists. I had the truck up on jacks to see if the u joints were binding but they seem fine. I was hearing a roar at the rear of the tranfser case. I pulled the tailshaft cover expecting to find a bad bearing but all is tight. It did look like a funny wear pattern was on the race within the tail shaftcover . The slip yoke is not smooth where it will contact the seal or the race.
Could a worn race cause a vibration at this point of the driveline and could it be a combination of race and slip yoke? Also, if the yoke is an issue, does it make sense to just put in a new cardan style driveshaft or just fix the old one? I have heard differing opinions about a 6" lift not needing the cardan style

 

[rampage]

What kind of lift (blocks, springs, shackle flip, etc)? Rear axle pinion rotated? Driveshaft lengthened? Need as much info about mods done for your lift. When going over 4" then it's a whole new ballgame.

And not that it matters to your problem, what kind of mods were done to the front? (i.e. Steering correction, frame bracing, driveshaft)