Gears

The best way to tell is to remove the rear cover and count the teeth on the ring and pinion gear and then divide the two.

Here is a guide to help you get the job done.

https://www.2carpros.com/articles/differential-service

GM had built a couple different set ups for the rear end. You can do one of two things: take your VIN number and call the dealership, they will give you more information you can think of. 2: look in your glove compartment and look for one of these RPO codes:

GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)

HC4 -- AXLE REAR, 4.56 RATIO

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken

I don't think that will work, you need to have the same gear ratio front and back or you will need really small tires up front.