ok I just got a 2000 wj with the I6 and selec trac with 105k on it my issue is the tcase will not get out of 4 part time when I shift it theres no light that turn on the dash but you hear it shift in to gear when you can get it to shift it make a metal on metal noise but when you go back into 4 part time it ok and also when its in 4 part time I checked in loose gravel only the rear tires are spinning

 

check the linkage, it may have come out of adjustment. Or your selector switch may be stuck on.

 

Yes, check the linkage. Also, the only light you'll get on the dash will be part-time 4WD. I haven't checked mine in 4WD low for a light yet. It may be hung up between full and part time. I believe the linkage is a cable on the WJ, however the anchor bracket may be bent or the cable mount loose. My 97 ZJ was out of adjustment, but you could feel the detents when it engaged different functions. That one was mechanical rod linkage.

I have a roll of florescent duct tape laying on my TC shift lever and when I go back to 2WD, I have to make sure it doesn't get hung up on the bezel or it will pop out of gear, back into part time.