I think you are talking about a 242 transfer case like is fitted to all 4.0 auto XJs. I am biased because it's what I own but I think it's the best transfer case option. It is a simple chain driven case, no viscous coupling to go wrong. The options are 2wd hi, 4wd hi with centre diff locked, 4wd hi centre diff unlocked for use on road (good on green lanes, in snow, wet etc.) and 4wd lo for proper offroading. Lots of choice for different conditions, simple like the 231 fitted to wranglers but with a 4wd setting suitable for road use.