You'll have to forgive me. I'm bitter from finding this on my girlfriend's tahoe last week and then having to fix it:

 

replaceable or not..i just always changed the hubs

 

my buddy has about 350,000 kms (approx 205,000 miles) and he beats the snot out of the truck, also a 99 5.3, still on original tranny motor and transfer case a rear end, still gets around 20 mpg highway

 

My 99 5.3 had 100k on it when i bought it and had 226 when i sold it. Original eng. trans t-case and got 19-20 mpg and i put 33s on it at 100k and worked the truck and ran like brand new when sold...minus the G80 exploding through the cover... oh well i did all maintainance on it and it lasted for me.