I have myself a 2004 Chevy Silverado 4x4 1500. I'm looking for the best way to decipher if it has a 8.5 or an 8.6 rear axle. It's a GT4 label with no other tags. And no tags on the rear cover. Needing to do a bearing kit. But I can't have it down for more than a day or two. So I need to have all the parts I need. Thank you anyone that can help!

 

As far as I know, your truck has an 8.6. I looked up your VIN#, turns out you have an identical truck as mine

So near as I can tell, you should have an 8.6, but you need to inspect the axle. If it has a drain plug on the bottom of the housing, looks like you have a 9.5" ring gear, if not it should be an 8.6". The only axle options available in the truck were 8.6, 9.5, 10.5, 11.5 and a 9.75 dana axle, which was only for quadrasteer trucks. Hope this answers your question.