Truck Forums - Im depressed and scared about 02 Allison Tranny wont shift

I just bought a 02 duramax with 119K LT crewcab 4x4. I'm fighting lymphoma and want to travel so I went to Palm springs and bought this truck.drove it home okay and now driving aROUND town tonight the tranny wouldn't shift out of, I think 3rd gear. 35 mph it was reading right at 2000 rpm and not shifting like it should have.Big noise when coming in and out of gear.Checked fluid and it was low about a pint I think. I have no experience with this Allison Tranny but the fluid was below the mark checked when HOT. The fluid seemed very thin but did not seem to smell. I have NO warning lights from any system.The message center has said nothing. I can't afford to have this broke already.Any ideas would be deeply appreciated.

Thank You,Chris:eek: