90 XJ 4 wheel not working. What to look for?

I'm new to the XJ. Just picked it up a week or so ago. The 4 wheel drive is "intermittent" at best, or doesn't work at all. I don't think 4 low ever worked, but 4 hi did for a few runs.

I put it on stands and it shifts into 4 hi, and the shaft is running to the front axle, but the wheels ain't turning.

All info is appreciated!

1990 Cherokee Laredo, 4.0 straight six. Auto trans, Transfer case and axles unknown.

Also, advise me on a cheap, easy way to lock the rear end. This Jeep is pretty much off-road only, so I'm not worried about street performance. I've got a 73 Commando with a spool I've been driving for years, so I'm used to it.

Sounds like the Central Axle Disconnect (CAD) may be malfunctioning. It could be internal to the CAD or that the vacuum line has a leak. There are kits to make the CAD cable operated or to permanently lock the CAD in position. You can also swap shafts from a non-CAD axle and block off the hole in the axle tube to eliminate it all together.

That was it. Thanks!

Went out, crawled under and the two-prong vacuum hose was knocked off. Plugged it back in and went out and climbed a steep ole' hill!

I found an article how to bolt the fork in place permanent like. I'll go that route when I get around to it.

Next stop: Rocket Science.

Yours, if still stock, is gonna have the Dana 35 c-clip rear axle. It's not known for its strength. There's no spool made for it to my knowledge and a a lunchbox locker start just over $200. Other than that are more expensive options or welding it.

Sent via messenger pigeon. I talk, he types.

Hey, I got a welder! ;)

Congrats, what are you going to make?

Lol, a locker!

Sent via messenger pigeon. I talk, he types.