What gears do I have?

How do I tell which gears my rear end has?

look in your glove box for these codes

GU2 = 2.73(only V8s)
GU4 = 3.08
GU5 = 3.23
GU6 = 3.42(came with Y87 option)


but a auto 3.8 should have 3.08's as stock unless it was a Y87 package