No four wheel drive. help!!

i have a 1990 cherokee sport with manual transmission. a couple of days ago i lost my four wheel drive. although when i pull the lever up to engage it, the part time light still comes on. also i can put the transfer case into netural and low gear, and the truck will move in low gear but the front wheels don't pull. i didn't hear anything obvious that anything broke. it just stopped working. could this be a vacuum problem, or something more serious. anyone have any ideas?

thanks

Brent

disco

Could be fartin in the breaze here, but do you have a Vac disconect front axle or no?

either a vac or mechanical problem... you have a disco dana 30 I assume.
quick checks to do. put T case in 4hi or low. jack up front passenger side of vehicle. with vehicle running reach underneath and spin the front drive shaft. no spin= T case engaged. now go to passenger side tire( the one thats off the ground) spin it... spins= non engagement of axle. check all your vac lines first they can be brittle and the plug at the end(that attaches to the motor dies easily) if you have a vac guage hook it up and confirm vacum (with the motor running). if vac looks good than it is most likely the shift fork. they are weak and problematic. to check that out you will need to remove the housing and motor. check for any play in the fork, play= bad. replace and should be good to go. when I have mine apart I just test the motor by hooking it up and engaging disengaging to watch the shaft slide back and forth.

just to narrow it down some more, my air hose rubbed through on my battery box, so sneak a peak there first, and listen carefully for air leaks. My air leak was really obviouse and I luckily found it while checking something else.

Could spray air lines down with soapy water to check for leaks better then listening.

I have an 87 XJ : Same thing happened to me. Took off the vacune shifter on the front, checked the fork, and discovered the shaft had a small amount of rust in it. Took it apart, and use 400 sand paper where the rust was, flushed with WD40 to clean it. Put it all back in and it has worked like a champ. Good Luck.

I have had this same problem in the past and it was the shift fork that had a small crack in it. It had just enough play so it would not go into 4 wheel drive, but the light still came on for me. Eventually the replacement aluminum fork started having issues again even though it was not broken or cracked. Just because of wear over time.

I just replaced my aluminum shift fork with a Dana Spicer 41553 steel fork. $17.61 from 6 States Distribution. It is amazing how much better the steel fork is, no more play and now it stays in 4 wheel drive. The nylon pads will work on the steel fork too. Replace it with a steel fork and forget about it.

When I got my 95 it had the same problem. I opened the transfer case (NP231) and the chain was off the sprockets. I don't know if this is common but assume it had just stretched enough to jump off. Rebuilt the case with new chain and it has worked great ever since.