Tech Questions about driveshaft on a 4" Teraflex lifted XJ

Did my lift, 4" Teraflex with arms etc..also installed about 1 1/4 of transfer case drop (homemade) but my rear driveshaft still vibrates-old u joints failed after first 300km of driving-surprisingly they were still original ones, YES, after 140 000 KM. Anyway lets get to the point ... i Come from YJ county and some serious offroading (went through 4 engines and 3 trannies) ... on my YJ i had a vacuum actuator on the axle, i looked under my new 98 XJ and noticed that i dont have one on the axle. Lifted my whole rig up and turned the passenger side wheel, and the front driveshaft turns. Does that mean that it turns all the time? It has to right? and its disengaged inside the Tcase? Also ... if thats the case ... it would cause vibrations and noise at the same speeds as the rear one?
Im asking because my XJ sounds like a TJ without the hard top and on 44 inch TSL Boggers... im thinking that vibration might damage the bearings on the tcase... whats your suggestion remedy to all these noises/vibrations? SYE for rear with CV... what about the front?

You are spot on about the axle.
It is called a 'non-disconnect' HP30, and the only way to stop the ds from turning is to remove it, or get a $900 set of hubs.
Remove one driveshaft at a time, or jack up the rear and drive it in 2wd, and see what shaft is causing the vibration.
If there are no vibes in 2wd with the rear lifted, then you need adjustable uppers to correct your pinion angle on the front.
My guess is that its the rear.
Now, with a 98 XJ, you are going to need an SYE at least 75% of the time with a lift anywhere over 3".
YMMV.
Also, your rear ds is in danger of coming off the shaft, even with the tcase drop.
Get an SYE, and odds are you will be set.
HTH.

I was looking at AA kit + Tom Woods DS, is that a good combo in your opinion? Also, what would happen if i took my stock DS and put a CV on top near the TC? without the SYE? i dont do any extreme Offroading with my XJ.

Tom wood's is the way to go. Great coustomer service, and a pretty cool guy to boot.

How does anyone else cope with the front shaft vibes? how is it on their rigs? I don't believe that a hub conversion is the only way to go, does everyone go the hub way? how about adding a cv joint on the shaft?

Castor and pinion angle is a compromise!Adjust it until you find that neutral zone and live with the rest.Front already has a DC joint and modifying a stock rear with a DC joint is just a lesson in futility and money!

Purple said:

How does anyone else cope with the front shaft vibes? how is it on their rigs? I don't believe that a hub conversion is the only way to go, does everyone go the hub way? how about adding a cv joint on the shaft?

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I once talked to both Tom Woods and Jesse at High Angle Driveline about a dual double cardan front driveshaft. Both companies said it could solve the problem (Tom Woods has done it before, and although Jesse hadn't made one for an XJ before, he didn't see any reason why it wouldn't work). They both said the shaft would be around $350+; It would still be half the cost of manual hubs.

I found its best to find a good compromise between castor and pinion angle.

Thanks guys thanks for all the info