It might have something to do with shaft RPMs. When I first started having the vibration when slowing down I put the truck on four jack stands and ran it through all speeds. Everytime on cost down it would shake the drive train as the RPMs slowed. If you have a long bed you can remove the rear half of the drive shaft and go front wheel drive to the parts store with no ill affects as a side note.

 

Thanks, I told NAPA about the 233-0188 and they said that they don't order that one anymore. They said that there was too many problems with it and now they use......I think he said 330A, but I'm not sure. Anyway, he ordered two of em for me. The one at the rear of the driveshaft and the one at the front of the rear driveshaft are real old, but the one in the middle looks shiny and new with a grease zirc too. Maybe this new part will fit better. It looks like it might be kinda hard to replace these. I remember changing u joints on the side of the road on those smaller trucks back in the day and it didn't take long at all. I'm gonna stop and get a 12 pk tomorrow cause it looks like I might need it for this job.

 

The culprit was the carrier bearing!