91 XJ 4x4 Problem

Hello, i just recently purchased this XJ 91 Cherokee Sport. Manual 5 speed, 4,0 HO motor. And the 4x4 is not working, and i am not too too familliar with 4x4 systems i havent worked on any yet.
I have noticed at times when i try and switch it into 4wd Hi or LO it does make a loud knocking/clacking noise and it feels like the 4x4 is working, but then it goes away and the 4x4 is not working. I have tried to search about this, and i am trying to figure out how this system works????? Does it have hubs? does it work on Vaccum lines? or are the front alxes always turning? i was not able to find out as they are so many confugrations!!! The basic conclusion is that the 4x4 doesnt work half of the time and or when it does engage it makes a hell alot of noise.

Any info or help would be greatly appreciated. Thanks

Also his weekend i have put it on the lift and raise the car and then put it in drive while in 4x4 selected and the front tires were NOT spining nothing from the front, but the back were fine. I also looked under the Jeep and the shaft that comes out of the transfer case to the front diff was turning! I dunno if that helps at all.

Thanks

I have also noticed that when i put it in 4hi or low the gear ratio changes!

You have a front axle vacuum disconnect. You have probably lost vacuum to the unit. Check this thread and it will give you more info. http://www.naxja.org/forum/showthread.php?t=73758&highlight=front+axle+disconnect

Your should also do a search on "front axle disconnect". There is a bunch of info pertaining to your unit. Discos were used from '84 to '91.

check your t-case fluid level and also check the t- case linkage for slop.

Jason

Ok cool, thanks, yeah i am reading up about the vaccum disconnect now, i understand how it works. I am just still stumped on why sometimes when it is in 4 hi or low that it makes that clacking noise??? COuld it be the fork that comes out of the vaccum disconnect?

The T-case fuild is fine, it has already been checked!

Hello! I'm having a similar problem with my 91 XJ. Does anyone know if it's possible to swap a t-case from an '89 Laredo to my 91 sport. I know there's alot of differences between the two as far as air intake is concerned but I can't seem to find any information on t-case idetification. Thanks.