Driveline problems

Ever since I bought my Jeep, I have always had problems with the driveline. I've taken it off numerous times to have it balanced, have checked the angles over and over again, and have lowered the transmission/adjusted the wedges on the springs accordingly. No matter what I do, I still seem to have driveline vibrations. They used to be so bad, that I would blow the u-joint on the tranny every 2,000 miles. That hasn't happened in a while, but I'm still getting vibrations when I hit around 30 mph. I've even considered tossing this driveline out and buying a new one, since this one has so many weights welded on it I doubt it will completely balance out anyway. Of course, before I drop 200 bucks into a new driveline, I wanted to see if anyone knew of something I might be missing here. I believe I have the correct angles on my driveline, but who knows, maybe I don't. What angles should a driveline have?

 

Is it in phase and are the angles the same?

 

Here's what appears to be a good source of tech info: http://www.4xshaft.com/techinfo.html
I have not read these articles, but the company has a good reputation. Might be worthwhile.

I'd think the first thing to do (if you haven't already) is remove the rear driveshaft and drive around in front wheel drive to see if the vibration goes away. Divide and conquer!

 

I had a shaft made with a CV joint. That cured my vibration problems. I'd suspect an extreme driveline angle, but with only a 2 1/2" shackle lift that doesn't seem likely. timgr's suggestion above would be worthwhile, just so you know for sure that it's in the rear shaft. Have you checked the condition of the crossmember mount. If it's real bad, it could cause a vibration. If you pull the rear driveshaft, check the pinion and the rear output bearing on the T case for looseness or slop. 1st thing to check is 73cj5's suggestion about the U Joints being "in phase". If the top and bottom U joints are out even one spline on the slip joint you'll get a vibration.