Dropping out of 4H

Hello All!

I have a stock 1996 Cherokee Sport, 4.0L-6 automatic, with just over 100,000 miles that I'm having a terrible time keeping in four wheel drive. After engaging 4H and moving a couple 100 feet (sometimes as much as a few miles) it feels like it slips back out with horrible thump followed by a bad grinding noise (more like a real-rapid clicking sound) It sounds like it coming from the transfer case.It's done this a couple of times over the winter but it seems to be happening more frequently. I have taken it to a transmission shop who can't recreate the problem, but has drained the transfer case. That didn't turn up anything; no leaks or burning smells, and the fluid was reddish clear with little or no metal shavings. I can't drive it this way with any kind of security, so I was wondering if there is anything specific I could have a shop look at? When shifting into gear the lever feels normal. Is there a linkage adjustment somewhere that could be slipping or broken?

Any help would be greatly appreciated.

Thanks,

JBXJ

I've had what would seem's to have been the same issue with my 87, I found that it was my tcase chain that had streached and would slip with a jumping clanking clicking sound. so I would say take a look at the tcase chain and the linkage to make sure no serious damage has occured. or take it to a shop to have them look at it