I've always generally been told anything over 3 to 3.5 inches you need the SYE and driveshaft. Especially if your going to add a 2" shackle. It would really suck to be out on the trail and the first time you have a lot of flex or suspension travel the drive shaft "slips" out and dups your trnafer case oil everywhere. Ive seen it happen and it isnt pretty.
88 YJ 6 cyl, 5 spd, RE 4.5" heavy-duty, Tom Woods driveshaft and SYE, 35x12.50 Goodyear MTR's on 15x8 black streetlock (simulated beadlock), and Pro-Comp MX-6 adjustable shocks
Converted A/C to engine driven air compressor.