Rear Axle Codes

Here is a table that gives the codes for different rear axle ratio, differential type, manufacturer, and build date information.  THe code is stamped on the right axle tube (as viewed from the front of the car) on the forward side.  It’s tough to see when it’s still in the car.  Of course some of the engine/tranny combinations listed were not available on the 78-83 Malibu.  But this will aid you in finding a rearend to swap into your Malibu. 

The first 3 digits indicate the axle code, the next one indicates manufacturer (B=Buick, O=Olds, C=Chevy, P=Pontiac), the next is Julian date it was built and the last it the shift it was made on. Limited slip rears had a tag on the differential cover that stated it needs posi fluid… that’s usually missing, if the cover has ever been off. However, a “B” in the axle code (i.e., 2BX) usually indicates a posi.

The 7.5″ rears have a differential cover that is smooth and kind of a squared off oval shape. The 8.5″ rears have a rounder shaped cover with a raisedhorizontal area in the middle.

1978

TransEngineRatioPeg LegLtd SlipStd/Opt
THM350196 “C”
49 State
2.732AB2BBSTD
THM350231 “A” Cal
49 State
2.732AB2BBSTD
THM350231 “A”
49 State
3.232AD2BDOPT
THM350231 “A”
49 State
2.412AJ2BJOPT
THM350231 “A”
Hi Altitude
3.232AD2BDSTD
THM350231 “G”
49 State
2.732AB2BBSTD
THM350231 “3”
49 State
2.732AB2BBSTD
Gear
Ratio
Ring
Gear
Assembly Codes
2.417.5″AZ, BZ
2.567.5″RY, SY, RC, SC, AA, BA
2.737.5″AX, BX, RS, SX, RD, SD, AB, BB
2.937.5″AG, BG
3.237.5″RU, SU, AU, BU, RG, SG

1979

TransEngineRatioPeg LegLtd SlipStd/Opt
THM3503.8 (LD5) A2.412AJ2BJSTD
THM3503.8 (LD5) A2.732AB2BBOPT
THM3503.8 (LD5) A3.232AD2BDOPT
THM3503.8 (LD5)
High Alt
3.232AD2BDSTD
THM3503.8 (LD5) A2.732RX2BXSTD
THM3503.8 (LD5) A3.232AU2BUOPT
THM3503.8 (LD5) A
Calif
3.232AU2BUOPT
THM3503.8 (LC6) 2
Calif
2.732AB2BBSTD
THM3503.8 (LC6) 2
Calif
2.732RX2BXSTD
THM3503.8 (LC8) 32.412AJ2BJSTD
THM3503.8 (LC8) 32.732AB2BBOPT
THM3503.8 (LC8) 33.082ACOPT
THM3503.8 (LC8) 32.412AJ2BJSTD
THM3503.8 (LC8) 32.732AB2BBOPT
THM3503.8 (LC8) 3
Calif
2.732AB2BBSTD
Gear
Ratio
Ring
Gear
Assembly Codes
2.147.5″RH
2.297.5″RA, AH, BH, AT, BT
2.417.5″AJ, BJ, AZ, BZ
2.567.5″RC, AA, BA, AY, BY
2.737.5″AX, BX, RX, RD, AB, BB
2.937.5″AG, BG
3.087.5″AC, BC
3.237.5″AD, BD, SC, RU, AU, BU, RG

1980

TransEngineRatioPeg LegLtd SlipStd/Opt
THM3503.8 (LC8) 32.416RB6BJSTD
THM3503.8 (LC8) 32.736AB6BBOPT
THM3503.8 (LC8) 32.736RD6BBSTD
THM3503.8 (LC8) 33.086ACOPT
THM3503.8 (LC8) 32.416RB6BJSTD
THM3503.8 (LC8) 32.736AB6BBOPT
THM3503.8 (LC8) 3
Calif
2.736AB6BBSTD
Gear
Ratio
Ring
Gear
Assembly Codes
2.297.5″AH, BH, AT, BT
2.417.5″AJ, BJ, AZ, BZ
2.567.5″AY, BY
2.737.5″AX, BX, RX, AB, BB
2.937.5″AG, BG, AW, BW
3.087.5″AC, BC, AV
3.237.5″AU, BU

1981

TransEngineRatioPeg LegLtd SlipStd/Opt
M64/Man 33.8 (LD5)3.088AC8BCSTD
2.418AJ8BJSTD
MX2/350C3.8 (LD5)3.088AC8BCOPT
3.238AD8BDOPT
MX2/350C
M33/350
3.8 (LC8)2.738AB8BBSTD
3.088AC8BCOPT
MV9/200C4.3 (LS5) Diesel2.298AH8BHSTD
Gear
Ratio
Ring
Gear
Assembly Codes
2.297.5″AH, AT, BH, BT
2.417.5″BJ, AJ, BZ, AZ
2.567.5″BY, AY
2.737.5″AB, BB, AX, BX, RX
2.937.5″AG, BG, AW, BW
3.087.5″AC, AV, BC
3.237.5″AU, BU

1982

TransEngineRatioPeg LegLtd SlipStd/Opt
2.412AJ2BJSTD
MX2/350C
M31/250C
3.8 (LD5)3.082AC2BCOPT
3.232AD2BDOPT
MX2/350C3.8 (LC8)3.082AC2BCSTD
MX2/350C4.1 (LC4)2.412AJ2BJSTD
MV4/350C
MV2/350C
5.7 (LF9)2.292AH2BHSTD
MV4/350C
MV2/350C
4.3 (LT6)
Diesel
2.412AJ2BJSTD
2.562AA2BAHi Alt STD
Gear
Ratio
Ring
Gear
Assembly Codes
2.417.5″BJ, AJ, BZ, AZ, BM, AM, CC, CQ, RZ, CU, RB, CH
2.567.5″BY, AY, CE, CN, CI, CV, BA, AA, RC, CL, CY, RY, RD, CM, CZ
2.737.5″AB, BL, AL, AX, BX, CW, CD, CR, BB, RX, CJ
2.937.5″AG, BG, AW, BW, RW
3.087.5″AC, BC, AV, RF, RV, BV
3.237.5″AD, BD, AU, BU, RG, RU, AE, BE

1983

TransEngineRatioPeg LegLtd SlipStd/Opt
2.412AJ2BJSTD
MX2/350C
M31/250C
3.8 (LD5)3.082AC2BCOPT
3.232AD2BDOPT
MX2/350C3.8 (LC8)3.082AC2BCSTD
MX2/350C4.1 (LC4)2.412AJ2BJSTD
MV4/350C
MV2/350C
5.7 (LF9)2.292AH2BHSTD
MV4/350C
MV2/350C
4.3 (LT6)
Diesel
2.412AJ2BJSTD
2.562AA2BAHi Alt STD
Gear
Ratio
Ring
Gear
Assembly Codes
2.417.5″RB, CC, AJ, AM, BM, CG, BJ, RZ, CH, AZ, BZ, CU, CK, CX
2.567.5″RC, CE, AA, CN, BA, CI, AY, CV, BY, RY, CL, CY
2.737.5″RD, CD, AB, AL, BL, CR, BB, RX, CJ, AX, CW, BX, CM, CZ
2.937.5″RE, AG, BG, RW, AW, BW
3.087.5″RF, AC, BC, RV, AV, BV
3.237.5″RG, AD, BD, RU, AU, BU
3.427.5″AE, RK, BE
3.737.5″AF, BF
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