There are guys on this site that can tell you just give them some time. I dont know what the number is on the transfer case but the 3/4 and 1 ton trucks came available with an electronic transfer case you could try googling "chevrolet 2500hd transfer case" and it would probably come up with a hit that would give you the actual transfer case number. Or heck even call a chevy dealer and they can tell you the umber on the transfer case. If you dont want to do that there is ls1tech and somebody over there can help you.