I have a 2002 Chevy Duramax that is now stuck in 4LO. I was driving it this morning at about 55 - 60 MPH and the Service 4WD Light came on briefly, it then slammed itself into 4LO. (How is that even possible?) After a brief moment of terror and hearing alot of nasty "ratcheting" noises, I pulled to the side of the road, placed the shifter into park and shut down the engine. I then restarted the truck to listened for noises. Everything sounded fine in Park,neutral and drive (at rest). 4 LO shifter light is lit and will not transfer into any other setting. I limped back home (3 miles) in 4Lo. The thing will not shift back out. Also, in Reverse, it will go about 10 feet, then coast to a stop...the R on the Column indicator will then start to flash. Can anyone advise me on what I should do? Thanks in advance for any help.