Thanks for your help.
I had the Jimmy towed to a transmission shop. They called me today and
said the truck already had a rebuilt transmission in it and they didn't
think that was the problem.
The guy said it was some kind of filter in the transmission plugged and
some seals were broken and that almost all of the fluid had drained
out. He said he had put some fluid in it this morning and drove it down
the road without a problem. So, he is going to replace the seals, clean
it out and something else i can't remember what he said...and it is
going to cost me about 850.00 less then i thought....great news : )