Mine is a 99. factory 4.10s I remember opening the glovebox when I was looking to buy it and saying "please say GT4, please say GT4!" and i was like "holy crap!! it says GT5!!!"

 

From my experience around here, most rcsb or rclb 4x4 with a 4.8 came with 4:10s, and most rcsb or rclb 4x4 with a 5.3 came with 3:73s like mine. Seemed like they used the 4:10s with the 4.8 to help in the get up and go department

 

I had a 2 wheel drive Z66 Avalanche with factory 4.10s, no one ever believed me but it was true.

 

my 00 2WD came with 3.73s which I always thought was weird. But thats pretty

 

maybe it tends to be 4:10s come with a 4.8 2wd or 4wd if not it must be completly random what gets what

 

Almost all of the 2002 Z71 Avalanches I looked at when I bought mine had 4.10s.