Ok, I've done some searching but haven't seen an answer. I'm new to the forum and it's been a while since I've had a Jeep. And my old 86 only had 2wd, 4full time, and 4lo. No 4hi. NP242? .... So, onto my new Jeep!

I just got an 87 xj. I'm told it has the NP231 t case. When driving home I decided to try the 4x4 again (slushy roads). I stopped at stop sign, lifted lever to 4hi and proceeded with my turn. The back end fishtailed out, obviously in 2wd still. But a half mile or so I could feel the Jeep tighten up as it engaged. At the next stop I put it into a nice four wheel drift confirming it was indeed in 4hi.

So I've had my fun, push the lever back to 2wd, but it stayed in 4hi. It bound up turning onto my street and again pulling in the drive. About an hour later I backed up, turning, and it was still binding, but when I turned the other way to drive down the drive it released.

Is it normal for the t case and front axle to take so long to disengage? I'm used to my pickup that shifts immediately.

Mine will usually do the same when it wants to try going straight down the road go like 5 MPH and throw it in nuetral and shift it 4 hi and then slam it into 2 hi and see if it disengages thats how i get mine out

Shift in and out of 4H at speed in a straight line. Lift off gas, pull lever into 4H, tap gas, let off gas, apply gas. Same thing going from 4H to 2H.

Thanx for the quick responses guys!! So, it is possible for the lever to move and the case to wait till things are lined up and unloaded to disengage. Like the forks are spring loaded or something.

And one other question, is this a "shift on the fly" system? I've always had to be at a stop or slow roll for my other 4x4s except my last Cherokee. But that one didn't matter too much as I could never get the vacume operated 2wd-4wd selector to work. So I just left it in full-time 4hi.

It was designed as "shift-on-the-fly". Except for shifting into 4low, it's the best way to shift them. With a 231 and a vacuum disconnect front axle, it's more necessary to shift on the fly so the vacuum actuated collar slides over and engages/disengages sooner.