ПОЛНЫЙ список разновидностей заднего моста и главной пары

YEAR
----
RPO Ring gear size in inches


1991
----
GM8 (2.56 ratio):
4GM 7.5
4ZH 8.5
4ZL 8.5*
4GA 7.5

GU2 (2.73 ratio):
4YL 8.5

GU4 (3.08 ratio):
4NC 8.5*
4LG 8.5
4LK 8.5
4NP 8.5*

GU5 (3.23 ratio):
4YM 8.5*
4YE 8.5
4LN 8.5*

GU6 (3.42 ratio):
4ZK 8.5
4ZJ 8.5*


1992
----
GM8 (2.56 ratio):
6ZA 8.5*
6ZC 8.5
6GD 7.5
6GE 7.5
6GM 8.5
6GK 8.5

GU2 (2.73 ratio):
6YL 8.5

GU4 (3.08 ratio):
6NC 8.5*
6LA 8.5
4NQ 8.5*
4LM 8.5
8NG 8.5*
8LM 8.5
8NQ 8.5*

GU5 (3.23 ratio):
6YF 8.5*
6YM 8.5*
6LN 8.5*
6GJ 8.5*
6YE 8.5
6YK 8.5*

GU6 (3.42 ratio):
6ZB 8.5*
6ZD 8.5
6GN 8.5
6GL 8.5*
6GP 8.5*
6GS 8.5


1993
----
GM8 (2.56 ratio):
6GM 8.5
8GD 7.5
8GE 7.5
6GK 8.5*

GU2 (2.73 ratio):
6YL 8.5

GU4 (3.08 ratio):
8LA 8.5
8NC 8.5*
8NG 8.5*
8LM 8.5
8LN 8.5*
8NQ 8.5*

GU5 (3.23 ratio):
6YE 8.5
6YM 8.5*

GU6 (3.42 ratio):
6GS 8.5
6GP 8.5*


1994
----
GM8 (2.56 ratio):
2YN 8.5

GU2 (2.73 ratio):
2GA 7.6
2GB 7.6
2GH 8.5

GW9 (2.93 ratio):
2YF 8.5
2LQ 8.5*
2YG 8.5*

GU4 (3.08 ratio):
2LW 8.5
2LX 8.5*

GU5 (3.23 ratio):
2LR 8.5
2ND 8.5*
2LY 8.5
2LZ 8.5*
2LT 8.5
2LS 8.5*
6YF 8.5


1995
----
GM8 (2.56 ratio):
2YN 8.5

GW9 (2.93 ratio):
2LQ 8.5*
2GF 7.625
2GG 7.625
4ZB 8.5
2YF 8.5
2YG 8.5*

GU4 (3.08 ratio):
2LW 8.5
2LX 8.5*
ZGH 8.5*

GU5 (3.23 ratio):
2LT 8.5
2LS 8.5*
2GU 8.5*
2LU 8.5*
2LY 8.5
2LZ 8.5*


1996
----
GM8 (2.56 ratio):
2YN 8.5

GW9 (2.93 ratio):
2LQ 8.5*
2GF 7.625
4ZB 8.5
2YF 8.5
2YG 8.5*

GU4 (3.08 ratio):
2LW 8.5
2LX 8.5*
2LL 8.5

GU5 (3.23 ratio):
2LT 8.5
2LS 8.5*
2GU 8.5*
2LU 8.5*
2LY 8.5
2LZ 8.5*

* = with Limited Slip "POSITRACTION"

EDIT: Note that the ring gear size code is NOT a RPO code that would appear on the vehicle RPO code list. Only the main gear option would appear (such as GU4 or GU5, for example, and G80 for posi). The ring gear codes (ie: 2LX) are actually part of the axle identification code used internally by GM. I verified this by looking on my decklid for all of my cars, and none of the sub-gear codes appear. Only G80 and GU4 appear, for example. This would explain much of the confusion, since there is no way to tell using your RPO tag unless you can find the codes stamped on the axle or actually measure your ring gear. This does tell us, however, that certain ratios ALWAYS got the 8.5" gear, for example, 3.08, 3.23 and 3.42 was never offered in anything else but a 8.5" gear in all those years. This is what I always held as being true but never could verify until now.