If there is wires plugging into the side of it, you have a 4L60E transmission. If there is no wire bundle, then its a 700R4 (doubtful that the previous owner swapped trannys)
Most tranny shops will let you cash and carry a rebuilt for $1000 cashola... Thats a good deal. You could try your luck with a junkyard trans but you might just get one thats no better than the one you are pulling.
If your fluid is burned smelling and very dark, then my first guess would be 3-4 clutch pack failure - requires a rebuild to repair.
Unplug your wire plug on the side of the transmission (or pull TRNS fuse), start the truck and put it in gear - can you drive it? I say this cause I think it starts out in 3rd gear by default when electrical connection is lost (which you force by unpluging or pulling the fuse). If you have no movement and it just revs up, then your clutches are toast and its time for the R+R. If it will drive, then your 3-4 servos are causing the problem, they are about 20 bucks and can be changed on the side of trans with it in the vehicle.
Go unplug that wire and report back to us with your findings.
Theres a few guys around here that know these trannys inside out, just give it a couple days and they will chime in with some help.
Last edited by ohsofly; 03-17-2012 at 03:40 PM.