Reference Manual

Chapter 3: Axles: Factory Useage

If a rear axle is known to be the original axle installed by the factory and the vehicle has a SPID, a simple method to determine the rear axle ratio would be to lookup the axle RPO.

2.14 G72 2.93 GU3
2.29 GH2 3.08 GU4
2.41 GU1 3.23 GU5
2.56 GM8 3.42 GU6
2.73 GU2 3.73 GT4
Positraction G80

Without a SPID or if it's possible the axle had been swapped at some point the axle code on axle can be used to determine the axle ratio.

Naturally, this assumes the original gears remain in the original housing.

Code Locations

axle code location

A manufacturer code will be metal stamped on the axle tube adjacent to the carrier for field identification. This code will be stamped on the right front inboard side, letters and numerals 1/4" high, 3" outboard of carrier and/or are located on a metal tag attached to a cover bolt.

Code Breakdown

axle code breakdown

A Body Axle Codes G Body Axle Codes

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