Gearbox transfer graunch bang

[simso]

Hey guys, Ive read a few posts of others with the same sort of problem, but no one has yet solved what it could be. I have a 98 XLT 5 spd manual, with the borg warner torque on demand transfer case. Sometimes when going into reverse on an angle that is around a corner or out of a driveway it kind of feels like a bump or even a gear graunch from the drivetrain gearbox trans and sometimes when driving and going aroun d a corner it does the same again. Now ive changed the oils as recommended by one of the guys here and checked for debris, which thank god I dont have. Troubleshooting this problem today, I put the car into 4wd high and when I was turning I got the horrible lurch graunch ect which I think is standard for turning in 4wd. But this is very similiar to the intermittent problem I have except that it only does it for a few seconds when not selected in 4wd
Any one got any recommendations. I have a feeling the transfer case is slipping me into 4wd occassionally whilst reversing turning ect can I disable this function, and is it normal for bad graunching whilst turning in 4wd
Any helps appreciated guys
Steve