Since this is one of the most neglected service usually.
What mileage would you suggest the lube be changed at?
3rd gens w/10 bolt or 9 bolt with functioning posi.
One person I met suggested 3000 mi.
I know sooner if you drive through deep water.

 

I usually change it about every 20k miles.

 

i think 30,000 would be a good interval and i tihnk that's what gm recommends