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

these numbers can be found in your glove box.example:my truck has a gt4 and g80(limited slip 3.73).just thought some of you would want to know this info.

 

Useful info ...

Is there a general listing of the RPO codes on this site?

 

http://www.c2e.info/rpocodes/

heres the site for info on all rpo codes for gm(should work for all i think 96 to present)

 

What is condsidered a "GQ1 -- AXLE REAR, STD RATIO"?

 

not positive but i think its open diff.with only passenger tire spins(aka:single tire fire)so if you have gq1 and gu4 that would be 3.08 gear with one wheel spin.