Ramsey said:
They are going to cram sye down your throat until you cant breathe. put the lift on first then see if you need it. i have the 3" and then i added 2" spacers and shackles and i still dont need one. just something to keep in mind. every jeep is different and of course ymmv.
An SYE is always a good choice unless you don't wheel it hard. The word "need" is subjective. Some of us need to fix problems before they create a serious situations and others need to roll the dice to save money.
Either way, people often talk only in terms of driveline vibration, but the stock design is a serious weak link that can be damaged offroad, particularly the '97+ design defect.
SYE's cure what is clearly a design defect (unsupported t-case output shaft on a relatively short driveline, which causes vibration and binding on many stock XJ's), and I'd put one a stock XJ. You add a lift, bigger tires, and sudden torque loads common in fourwheeling, and not spending the money up front on an SYE is nothing but a gamble on having to spend even more on case repairs, not to mention major damage may mean leaving your rig on the trail.
I spent a grand fixing the transfer case on my '97 because that flimsy, unsupported output shaft bent on a 2-3 rated trail. We hit some deep, wet, unexpected snow (March in Virginia) that took a major rescue operation and a lot of subsequent throttle to get out of. Nothing that in retrospect should have caused driveline damage, but it did.
The SYE is the only way to both fix the weak link and prevent vibes, and IMO should be part of any lifted design on a late model XJ (and is a very good idea on earlier model XJ's that see heavy offroad use).
Nay