The easiest way to find out which rear end gear ratio your van has is to look in your glove box at the RPO sticker.  The RPO codes will tell you ALL of your vans specific options including your rear end gear ratio.

 

CLICK ABOVE TO SEE A RPO STICKER FROM A 1989 ASTRO/SAFARI VAN

 

RPO AXLE CODE LIST BELOW:

GU2 2:73 ratio

GU4 3:08 ratio

GU5 3:23 ratio

GU6 3:42 ratio

GT4 3:73 ratio

GT5 4:10 ratio

GQ1 Open Differential Rear Axle

G80 GOV-LOC Rear Axle

 

NOTE!   The RPO CODE on the sticker only shows which rear axle was installed at the factory.  If you are not the original owner of your van you don't know for sure if the axle has been replaced or not.  The only way to be SURE what your rear axle ratio is will be to look at the actual factory code stamped on the axle itself. 

 

CLICK ABOVE TO SEE A VIDEO OF HOW THE FACTORY G80 GOV-LOC UNIT WORKS

 

 

 

CLICK ABOVE TO SEE WHAT A STANDARD REAR END LOOKS LIKE

 

 

 

CLICK ABOVE TO SEE WHAT A G80 GOV-LOC REAR END LOOKS LIKE

 

 

AXLE TUBE CODES

CLICK ABOVE TO SEE WHERE YOU WILL FIND THE AXLE CODE STAMP ON A 1989+ ASTRO/SAFARI VAN

 

The surefire way to find out which gear ratio your rear axle has is to look at the spot you see pointed out in the image above. The parking brake cable runs right across the area you need to see.  You will need to clean off the axle tube well to see the letters-numbers clearly.  You will notice the code is located on the front of the tube on the passengers side of the van. However, I have found that on 1988 and older, the code is found on the front of the drivers side axle tube.

 

 

NOTE!  The first 3 letters of the code stamp are the ones that matter.  Just compare them to the list provided below to determine you gear ratio.

FAA: 7.5", 2.56 open (1985-1986 Astro)
FAF: 7.5", 2.73 open (1988 Astro)
FAG: 7.5", 3.08 open (1988-1989 Astro)
FAH: 7.5", 3.42 open (1988-1989 Astro)
FAJ: 7.5", 2.73 posi (1988 Astro)
FAK: 7.5", 3.08 posi (1988-1989 Astro)
FAL: 7.5", 3.42 posi (1988-1989 Astro)
FAM: 7.5", 3.73 open (1988-1989 Astro)
FAN: 7.5", 3.73 posi (1988-1989 Astro)
FAP: 7.5", 4.10 open (1988-1989 Astro)
FAR: 7.5", 4.10 posi (1988-1989 Astro)
FAS: 7.5", 3.23 open (1988-1989 Astro)
FAT: 7.5", 3.23 posi (1988-1989 Astro)
FBA: 7.5", 2.56 posi (1985-1986 Astro)
FCA: 7.5", 2.73 open (1985-1987 Astro)
FCB: 7.5", 2.73 posi (1985-1986 Astro)
FFA: 7.5", 3.08 open (1985-1987 Astro)
FFB: 7.5", 3.08 posi (1985-1986 Astro)
FMA: 7.5", 3.42 open (1985-1987 Astro)
FMB: 7.5", 3.42 posi (1985-1986 Astro)
FRA: 7.5", 3.73 open (1985-1987 Astro)
FRB: 7.5", 3.73 posi (1985-1986 Astro)
FSA: 7.5", 4.11 open (1985-1986 Astro)
FSD: 7.5", 4.11 posi (1985-1986 Astro)

GWH: 7.5", 4.10 open (1985-1987 Astro)
GWJ: 7.5", 4.10 posi (1985-1986 Astro)

HZA: 7.5", 2.73 posi (1987 Astro)
HZB: 7.5", 3.08 posi (1987 Astro)
HZC: 7.5", 3.42 posi (1987 Astro)
HZF: 7.5", 3.73 posi (1986 Astro)
HZG: 7.5", 4.11 posi (1986-1987 Astro)

KJM: 7.5", 2.73 open (1987 Astro)
KJN: 7.5", 3.08 open (1987 Astro)
KJP: 7.5", 3.42 open (1987 Astro)
KJR: 7.5", 2.73 posi (1987 Astro)
KJS: 7.5", 3.08 posi (1987 Astro)
KJT: 7.5", 3.42 posi (1987 Astro)
KJU: 7.5", 3.73 open (1987 Astro)
KJW: 7.5", 3.73 posi (1987 Astro)
KJX: 7.5", 4.10 open (1987 Astro)
KJY: 7.5", 4.10 posi (1987 Astro)
KRK: 7.5", 2.73 open (1987 Astro)
KRL: 7.5", 3.08 open (1987 Astro)
KRM: 7.5", 3.42 open (1987 Astro)
KRN: 7.5", 2.73 posi (1987 Astro)
KRP: 7.5", 3.08 posi (1987 Astro)
KRR: 7.5", 3.42 posi (1987 Astro)
KRS: 7.5", 3.73 open (1987 Astro)
KRT: 7.5", 3.73 posi (1987 Astro)
KRU: 7.5", 4.10 open (1987 Astro)
KRW: 7.5", 4.10 posi (1987 Astro)

PZK: 7.625", 4.10 open (1990 Astro)
PZL: 7.625", 4.10 posi (1990 Astro)

RHB: 7.625", 3.23 open (1990 Astro)
RHC: 7.625", 3.23 posi (1990 Astro)
RHD: 7.625", 3.42 open (1990 Astro)
RHF: 7.625", 3.42 posi (1990 Astro)
RHG: 7.625", 3.73 open (1990 Astro)
RHH: 7.625", 3.73 posi (1990 Astro)
RHL: 7.625", 3.23 open (1990 Astro)
RHM: 7.625", 3.42 open (1990 Astro)
RHN: 7.625", 3.73 open (1990 Astro)
RHP: 7.625", 3.23 posi (1990 Astro)
RHR: 7.625", 3.42 posi (1990 Astro)
RHS: 7.625", 3.73 posi (1990 Astro)
RHT: 7.625", 4.10 open (1990 Astro)
RHU: 7.625", 4.10 posi (1990 Astro)

SGF: 7.625", 3.23 open (1991 Astro)
SGG: 7.625", 3.23 posi (1991 Astro)
SGH: 7.625", 3.42 open (1991 Astro)
SGJ: 7.625", 3.42 posi (1991 Astro)
SGK: 7.625", 3.73 open (1991 Astro)
SGL: 7.625", 3.73 posi (1991 Astro)
SGM: 7.625", 4.10 open (1991 Astro)
SGN: 7.625", 4.10 posi (1991 Astro)
SGS: 7.625", 3.23 open (1991 Astro)
SGT: 7.625", 3.23 posi (1991 Astro)
SGU: 7.625", 3.42 open (1991 Astro)
SGW: 7.625", 3.42 posi (1991 Astro)
SGX: 7.625", 3.73 open (1991 Astro)
SGY: 7.625", 3.73 posi (1991 Astro)
SHD: 7.625", 3.23 open (1990 Astro)
SHF: 7.625", 3.23 posi (1990 Astro)
SHG: 7.625", 3.42 open (1990 Astro)
SHH: 7.625", 3.42 posi (1990 Astro)
SHJ: 7.625", 3.73 open (1990 Astro)
SHK: 7.625", 3.73 posi (1990 Astro)
SHL: 7.625", 4.10 open (1990 Astro)
SHM: 7.625", 4.10 posi (1990 Astro)
SHR: 7.625", 3.23 open (1990 Astro)
SHS: 7.625", 3.23 posi (1990 Astro)
SHT: 7.625", 3.42 open (1990 Astro)
SHU: 7.625", 3.42 posi (1990 Astro)
SHW: 7.625", 3.73 open (1990 Astro)
SHX: 7.625", 3.73 posi (1990 Astro)
SHY: 7.625", 4.10 open (1990 Astro)
SHZ: 7.625", 4.10 posi (1990 Astro)

TZD: 7.625", 3.23 open (late 1995 Astro)
TZF: 7.625", 3.23 posi (late 1995 Astro)
TZG: 7.625", 3.42 open (early 1995 Astro)
TZH: 7.625", 3.42 posi (late 1995 Astro)
TZJ: 7.625", 3.73 open (late 1995 Astro)
TZK: 7.625", 3.73 posi (late 1995 Astro)

USN: 7.625", 3.23 posi (1993-early 1995 Astro)

UTM: 7.625", 3.23 posi (1991-1992 Astro)
UTN: 7.625", 3.42 posi (1993-early 1995 Astro)
UTP: 7.625", 3.42 posi (1991 Astro)
UTR: 7.625", 3.73 open ('91-early '95 Astro)
UTS: 7.625", 3.73 posi ('91-early '95 Astro)
UTT: 7.625", 3.23 open (1991-1992 Astro)
UTU: 7.625", 3.23 posi (1991-1992 Astro)
UTW: 7.625", 3.42 open (1991-1992 Astro)
UTX: 7.625", 3.42 posi (1991-1992 Astro)
UTY: 7.625", open (1991-1992 Astro)
UTZ: 7.625", 3.73 posi (1991-1992 Astro)

VAC: 7.625", 3.23 open (1996-1997 Astro)
VBC: 7.625", 3.23 posi (1996-1997 Astro)
VCC: 7.625", 3.42 open (1996-1997 Astro)
VDC: 7.625", 3.42 posi (1996-1997 Astro)
VFC: 7.625", 3.73 open (1996-1997 Astro)
VGC: 7.625", 3.73 posi (1996-1997 Astro)
VKA: 7.625", 3.42 posi (1995 Astro-Export)
VKC: 7.625", 3.42 posi (1996-1997 Astro-Export)
VLA: 7.625", 3.73 posi (1995 Astro-Export)
VLC: 7.625", 3.73 posi (1996-1997 Astro-Export)

 

PLEASE!!  If you find any of this information to be incorrect, please contact us immediately so we can make any necessary changes.