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

Trans Engine Ratio Peg Leg Ltd Slip Std/Opt
THM350 196 "C"
49 State
2.73 2AB 2BB STD
THM350 231 "A" Cal
49 State
2.73 2AB 2BB STD
THM350 231 "A"
49 State
3.23 2AD 2BD OPT
THM350 231 "A"
49 State
2.41 2AJ 2BJ OPT
THM350 231 "A"
Hi Altitude
3.23 2AD 2BD STD
THM350 231 "G"
49 State
2.73 2AB 2BB STD
THM350 231 "3"
49 State
2.73 2AB 2BB STD

 

Gear
Ratio
Ring
Gear
Assembly Codes
2.41 7.5" AZ, BZ
2.56 7.5" RY, SY, RC, SC, AA, BA
2.73 7.5" AX, BX, RS, SX, RD, SD, AB, BB
2.93 7.5" AG, BG
3.23 7.5" RU, SU, AU, BU, RG, SG

 


1979

Trans Engine Ratio Peg Leg Ltd Slip Std/Opt
THM350 3.8 (LD5) A 2.41 2AJ 2BJ STD
THM350 3.8 (LD5) A 2.73 2AB 2BB OPT
THM350 3.8 (LD5) A 3.23 2AD 2BD OPT
THM350 3.8 (LD5)
High Alt
3.23 2AD 2BD STD
THM350 3.8 (LD5) A 2.73 2RX 2BX STD
THM350 3.8 (LD5) A 3.23 2AU 2BU OPT
THM350 3.8 (LD5) A
Calif
3.23 2AU 2BU OPT
THM350 3.8 (LC6) 2
Calif
2.73 2AB 2BB STD
THM350 3.8 (LC6) 2
Calif
2.73 2RX 2BX STD
THM350 3.8 (LC8) 3 2.41 2AJ 2BJ STD
THM350 3.8 (LC8) 3 2.73 2AB 2BB OPT
THM350 3.8 (LC8) 3 3.08 2AC --- OPT
THM350 3.8 (LC8) 3 2.41 2AJ 2BJ STD
THM350 3.8 (LC8) 3 2.73 2AB 2BB OPT
THM350 3.8 (LC8) 3
Calif
2.73 2AB 2BB STD

 

Gear
Ratio
Ring
Gear
Assembly Codes
2.14 7.5" RH
2.29 7.5" RA, AH, BH, AT, BT
2.41 7.5" AJ, BJ, AZ, BZ
2.56 7.5" RC, AA, BA, AY, BY
2.73 7.5" AX, BX, RX, RD, AB, BB
2.93 7.5" AG, BG
3.08 7.5" AC, BC
3.23 7.5" AD, BD, SC, RU, AU, BU, RG

 


1980

Trans Engine Ratio Peg Leg Ltd Slip Std/Opt
THM350 3.8 (LC8) 3 2.41 6RB 6BJ STD
THM350 3.8 (LC8) 3 2.73 6AB 6BB OPT
THM350 3.8 (LC8) 3 2.73 6RD 6BB STD
THM350 3.8 (LC8) 3 3.08 6AC --- OPT
THM350 3.8 (LC8) 3 2.41 6RB 6BJ STD
THM350 3.8 (LC8) 3 2.73 6AB 6BB OPT
THM350 3.8 (LC8) 3
Calif
2.73 6AB 6BB STD

 

Gear
Ratio
Ring
Gear
Assembly Codes
2.29 7.5" AH, BH, AT, BT
2.41 7.5" AJ, BJ, AZ, BZ
2.56 7.5" AY, BY
2.73 7.5" AX, BX, RX, AB, BB
2.93 7.5" AG, BG, AW, BW
3.08 7.5" AC, BC, AV
3.23 7.5" AU, BU

 


1981

Trans Engine Ratio Peg Leg Ltd Slip Std/Opt
M64/Man 3 3.8 (LD5) 3.08 8AC 8BC STD
MX2/350C 3.8 (LD5) 2.41 8AJ 8BJ STD
3.08 8AC 8BC OPT
3.23 8AD 8BD OPT
MX2/350C
M33/350
3.8 (LC8) 2.73 8AB 8BB STD
3.08 8AC 8BC OPT
MV9/200C 4.3 (LS5)
Diesel
2.29 8AH 8BH STD

 

Gear
Ratio
Ring
Gear
Assembly Codes
2.29 7.5" AH, AT, BH, BT
2.41 7.5" BJ, AJ, BZ, AZ
2.56 7.5" BY, AY
2.73 7.5" AB, BB, AX, BX, RX
2.93 7.5" AG, BG, AW, BW
3.08 7.5" AC, AV, BC
3.23 7.5" AU, BU

 


1982

Trans Engine Ratio Peg Leg Ltd Slip Std/Opt
MX2/350C
M31/250C
3.8 (LD5) 2.41 2AJ 2BJ STD
3.08 2AC 2BC OPT
3.23 2AD 2BD OPT
MX2/350C 3.8 (LC8) 3.08 2AC 2BC STD
MX2/350C 4.1 (LC4) 2.41 2AJ 2BJ STD
MV4/350C
MV2/350C
5.7 (LF9) 2.29 2AH 2BH STD
MV4/350C
MV2/350C
4.3 (LT6)
Diesel
2.41 2AJ 2BJ STD
2.56 2AA 2BA Hi Alt STD

 

Gear
Ratio
Ring
Gear
Assembly Codes
2.41 7.5" BJ, AJ, BZ, AZ, BM, AM, CC, CQ, RZ, CU, RB, CH
2.56 7.5" BY, AY, CE, CN, CI, CV, BA, AA, RC, CL, CY, RY, RD, CM, CZ
2.73 7.5" AB, BL, AL, AX, BX, CW, CD, CR, BB, RX, CJ
2.93 7.5" AG, BG, AW, BW, RW
3.08 7.5" AC, BC, AV, RF, RV, BV
3.23 7.5" AD, BD, AU, BU, RG, RU, AE, BE

1983

Trans Engine Ratio Peg Leg Ltd Slip Std/Opt
MX2/350C
M31/250C
3.8 (LD5) 2.41 2AJ 2BJ STD
3.08 2AC 2BC OPT
3.23 2AD 2BD OPT
MX2/350C 3.8 (LC8) 3.08 2AC 2BC STD
MX2/350C 4.1 (LC4) 2.41 2AJ 2BJ STD
MV4/350C
MV2/350C
5.7 (LF9) 2.29 2AH 2BH STD
MV4/350C
MV2/350C
4.3 (LT6)
Diesel
2.41 2AJ 2BJ STD
2.56 2AA 2BA Hi Alt STD

 

Gear
Ratio
Ring
Gear
Assembly Codes
2.41 7.5" RB, CC, AJ, AM, BM, CG, BJ, RZ, CH, AZ, BZ, CU, CK, CX
2.56 7.5" RC, CE, AA, CN, BA, CI, AY, CV, BY, RY, CL, CY
2.73 7.5" RD, CD, AB, AL, BL, CR, BB, RX, CJ, AX, CW, BX, CM, CZ
2.93 7.5" RE, AG, BG, RW, AW, BW
3.08 7.5" RF, AC, BC, RV, AV, BV
3.23 7.5" RG, AD, BD, RU, AU, BU
3.42 7.5" AE, RK, BE
3.73 7.5" AF, BF

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