M1009 vibration

[2deuce]

I have parked this truck for the last 2 years and bought a little 91 G-10 Chevy shorty van, because I couldn't figure this vibration out. The van is very handy, low miles, rust free, economical and was cheap, but I want to fix this CUCV. This is the nicest looking, rust free M1009 I have ever owned. I bought new motor mounts, but returned them, because the mounts in there are solid. I couldn't get them to move. The balancer runs true, but not knowing why I have this vibration, I thought I'd change it. I put the CUCV in a place where I could work on it in my spare time. Yesterday I jacked up the rear so I could run it and see if the vibration was in the drivetrain. This is something I consider dangerous and not comfortable doing, but I'm desperate. As soon as the rear wheels started spinning I could feel it. The driveline looked bent, but it was rebuilt. I got under there and removed the driveline and found the u-joint straps were worn. They were letting the u-joint slip in the yoke. They were tight, but not doing their job. I didn't know if the worn out straps were the cause or a symptom of the vibration. I had pulled on the driveline in the past and couldn't get any movement so I thought they probably were a symptom. I got new straps and the driveline still looked bent while running, but not as much movement with the new straps, and the vibration was improved. With the driveline still bolted up, but everything stopped, my son said he thought the yoke didn't look true and he wasn't under the truck. I was under there and I didn't notice it but he was right. He has a good eye. I removed the yoke on the rear end and can see it is bent. Bent yoke is the cause. Since it is the 4th I won't be able to get another yoke until tomorrow but I'm 100% sure a new yoke will fix this. I hope this helps someone in the future. Maybe this is not that uncommon, but a bent yoke is a 1st for me. Thanks to everyone who posted and tried to help, I really appreciate it.