[Darwood]

I would say save the $100 you would spend on new u-joints and save up for a front Double Cardan shaft. There really isn't much you can do other than lower the rig, or get rid of the caster correction. I installed new u-joints in my rear shaft and it did nothing to help my current rear shaft vibration problems.

Going 2wd would be a good temporary solution. Heck just pull the front drive shaft and be done with it for now. No need to install locking hubs (unsless you want to).

Most likely it isn't your rear shaft however it could be. I'm now convinced I was getting rear driveshaft vibrations with just J springs in the rear. If I pulled my Double Cardan front shaft and locked the transfercase the vibes would go away, but I'm pretty sure it was the rear shaft that was vibrating. It would just act up when the transfer case wasn't locked. Probably something to do with the torque.

Right now I'm saving for a rear Double Cardan seeing as I still have some rear vibrations even after adjusting my pinion angle with the rear upper control arms.

Some trucks are just more susceptible to vibrations than others. mine for example is a prime candidate for vibrations for some reason.