Post Bastard Pak

My 96 xj is my DD with 130k, 5spd and was all stock until I put the bastard paks on the rear and OME 930's on the front yesterday. I used practically new s10 paks mated to my main leafs and the installation was based on info gathered here ($11 Bas Pak threads & others). My original leaves were pretty flat and my measurement from hub center to bottom of flare stood at 15 inches. Front stood at 17 inches. I carry tools, occasional lumber and maybe 350 additional pounds in the roof rack, hitch, rear carrier and front grill guard. After install, rear measurement is right at 20 inches and front just over 19 inches. Took it for a 45 mile test drive and noticed some vibration coming from the rear and loss of some accelleration power as well. The sound is similar to that coming from aggressive tire tread on pavement though it can also be felt through my stick. I am worried that the change in angle for the drive shaft may cause damage at the rear diff even though this lift technically falls into 2.5 to 3 inch range before settling. I need input as to where to direct my efforts at eliminating the vibes. My thinking has me looking at rear shims forcing the diff upward a bit. I was hoping not to have to drop the TC and lose that clearance.
Or could there be another issue here....like the driveshaft out of whack due to some manipulation with the rear leaf pak placement. I don't want to drive it until I figure out what's up so any help from naxja folk would be welcome. Thanks.

If you notice the vibe, more, when braking (tail end raises) it could be that you have exceeded the angle of the slip yoke.
Simple test. Jack up the rear and leg the axle droop. Turn drive shaft. Check for binding.
Also check ujoints for play.

I have a 96 also ,went up with the pinion, it in fact needs to go down 2 degrees or so below the tcase angle.
It doesnt work. I didnt try the tcase bandaid drop so i went with the highly recommended Tom Woods sye setup. I will know after this weekend
525 bucks but if it does the job then it should be the do it and forget thing,,i hope.

After talking with xj friends and researching further, I went ahead and lowered the transfer case an inch using some square stock and longer bolts. That eliminated over 90% of the vibes I was getting as it allowed the yoke and boot to regain proximity to the TC. Used metric bolts 10mm x 50 mm coarse thread.
To remove the threaded post, I brought the nut out flush, grooved the top with a grinder, and did a quick weld to the groove. Both threaded posts came out without a hitch as the welding heat helped the process.
I am guessing that as the rear springs relax, any remaining vibes will also be gone. Sure did not want to go the $525 sye route. Thanks for your input.

Tracked down some 2* shims and installed them this evening. Test drive showed that performance is back to stock. Measurement after shims at rear showed 20.5 inches from mid point to flare. I fabbed up some basic shock extenders out of square stock and angle iron that compensated for a 3 inch lift change and allows me to keep my low mileage SensaTracs. Last items to address include a longer hydraulic brake line in back and reworking the e-brake lines since they are both maxed out by the lift. But I do want to look closely at the lower control arms up front to see if any adjustment is necessary. This process is definitely not brain surgery but it taught me a lot about my suspension and demonstrated how interconnected all the systems are at chassis level. And then there's this hypothesis that the better you can see beneath your vehicle, the more likely you are to maintain it. I hope.

One last update on the bastard pak lift. A week later and I was still having some slight vibes in the drive shaft until a friend told me to try taking out the overload leaf at the bottom of the pak. He felt it to be pretty useless considering the spring arc and the half inch loss could benefit the pinion angle. He was right. The total effect of the TC drop, 2* shims and removal of overload leaf was exactly what was needed to get the balance. Removing center pins was a pita and I had to fab a replacement due to thread damage during removal. Kept the 2* shims and the test drive was excellent. The s10 leafs are strong and I don't see a need for the overload leaf at all. Maybe I will replace it in a couple years if or when they begin to sag..
My ride with the extended sensatrac shocks might not be escaladeable but I would compare it to a relatively new f150. Probably the extra weight I carry is a good balance for the HD s10 leaf pack. All in all, doing the bastard pak is a major improvement over stock leaf springs and it is done as cheaply as it can be done. Since I fabbed my shock extenders and reused the year old Monroe shocks, I figure the total lift cost to be right at $200. That figure covered new front coils and almost new springs, new hardware, shims and steel. I guess I'm damn lucky I work for free.