Identifying axles & Gear changes

[Black Widow Silverado]

I have an 87 chevy silverado with 10 bolt front and rear axles and I was wondering on average what does it cost to get the gears changed? How do I identify my axles do the numbers on the axle tell me the ring gear size what do the numbers tell me ?

[LS1Steve]

pretty easy to tell what gears you have, just jack it up.

when its up in the air, block one tire so it doesn't move. Put a marker on the driveshaft, then spin the tire one complete rotation and count how many times the driveshaft spins. If it spins about 3 1/4 turns, you have a 3.23:1, if it spins about 3 1/2 turns, a 3.42:1, 3 3/4=3.73:1, etc...