New Process Transfer case
 

I have a 2004 Sierra 2500HD and I use it as a work/plow truck. 163,xxx miles and runs flawless. My question is, when I plow up against a snow bank or back-up rapidly I get a series of loud bangs from under the truck in the area of the transfercase. Is it possible or likely that the chain is jumping on the sprockets? If not what might this noise be from? Thank-you

When your NOT in 4X4... and you perform the same actions. Do you still get that loud bangs?
If not, I would say your right. Chain has worn and stretched and now with the loud bangs, your sprockets are worn now too.

I only get the banging when it is 4x4. Now the next question, Other than a GMC dealer where do you recommend getting a new chain? I am not sure if you can replace the gears separate from the shafts. Everywhere I have looked they do not list the gears. Also is this a 1 1/4 or 1 1/2 wide chain? No one can tell me that either. Thanks Jeff

I would recommend.. take your VIN number of your 2004 Sierra 2500HD to your dealership and get them to run the number in their computer to find out which T case you have in your truck.
Then pick their brains on getting some prices on that chain and sprockets.

Then when you start shopping for prices... You'll have a better idea whether your getting a good price or not.