drive without rear drive shaft

So I was driving home from a camping trip this weekend and heard a pop followed by a lot of thuds. Stopped and walked back 50 feet to pick up my drive shaft since the u-joint broke. I sealed up the t-case (89 231) with a trashbag and duct tape to keep fluid from leaking and put it in four wheel drive. Nothing happens. I look underneath it and the front drive shaft is spinning but nothing is happening. I have the disco axle, so if the vacuum wasn't engaging would that be the reason why it wouldn't work?

Yup! It's either not fully engaged, or the vacuum actuator failed....well that, or the plug just fell off....seen that more than once on YJs.

you can open up the hatch, its only 4 bolts and manually actuate it. I think you can then readjust the fork on the hatch and slap it all back together.