mellowme

Hello, I have a 99 sub that the service 4WD light came on about two weeks ago. I tried shifting from 2WD to 4WD and 4 low it would go into 4hi and back to 2wd but not 4lo then quit doing any thing no lights no shift noise. The wife drove it Saturday and she said when she started it there was a loud noise then it had no drive no reverse. She had it towed to the house and she said it will roll in park so I am thing t case. Any ideas on how to diagnose, what to look for first? I am out of town and have not seen it yet, but was looking for ideas on where to start.

Thanks