t-case question

well I have a few questions???
I have noticed that there is what looks to be some fluid that has leaked out of the rear output shaft of my 97 xj 4.0, np231 tcase. after I lifted it to 3" using a Super lift, it pulled the rear slip yoke out a bit and was causing a whole bunch of vibs. so I had a shop lengthen the rear DS to make it fit better, and I still have some vibs.
could the slip yoke be damaged? causing the vibs? I checked the fluid level in the tcase and its full. the fluid has been sprayed on the undercarage form pass-drivers side...but nothing is dripping???? could i need to get a AA HD SYE and new DS from Tom Woods or a RE hack-n-tap???
BTW there is some sound that sound like huge Mud tires but I have not installed new tires since the lift, also it kinda sounds like somewhat of a metal sound or something like that. I checked the rear trans mount, and it looks good. Also i removed the Front DS and the sound was still there, pinion should be correct and ujoints have been all replaced, along with the rear wheel bearings, poly bushings were used and full leafs were installed in the rear. And i have a Tcase drop on its way.
So what should I do.

I would look at the seal first, it may be bad. I have the superlift 3" on my 93 and have had no such issues.

dc changed somthing for the (iirc)96+ that gave people tons of problems with small lifts

pre 96 4" lift with no problems(most of the time)
96+ 2"lift could give you problems

your t/c drop should help but it is just a band aid, you should be looking into a sye and custom shaft especially if you want to go higher

mike