The vibration was finally fixed with the replacement of the motor mounts. I did replace all of them but it was definitely the driver's side mount that was causing the extreme vibration when I shifted out of park or neutral. That vibration was felt through my seat and did seem to vibrate mostly the rear end area.
After I replaced that mount, I could see that there was no rubber at all between the center rod and the outer area of the mount so the motor would twist along with the drive shaft as the jeep was put under load. It was a pita to change since I was by myself. I had a hard time getting the center bolt out since nothing was holding it. It came out all the way to the threaded ends and I had to get a small sledge hammer and a flat prybar to bang it out and there's not much room in there to work. Putting the new one in was a matter of constantly adjusting my floor jack to line up the hole just right to get that center bolt back in. Thats where a helper would have been handy since I could see the hole from underneath lying just behind the front left tire. My floor jack was holding although from the front where I had the jack handle I didn't have a good view of the mount.
Dusterdude, yea, that PB Blaster did a good job, thanks. That stuff is great.
Polkapower, the price was right with those mounts from Rockauto and since I'm budgeting, the jeep was free and and I don't know what other expenses I'll see with this jeep, I went for the price. I'll be more than willing to do the job again with a better quality mounts when I see the jeep is running fine.
I appreciate everybody's input and especially this site. I plan to be here alot.
I don't know if anybody here has used it but there is a product that restores and preserves rubber well. Its called AT-205 re-seal
. I think it strengthens rubber and helps restore old bushings and things (but it will eat plastic) and I'll be spraying it on the rubber there to see if it gives the mounts a longer lifespan.