I 1978 CHEVROLET TRANSMISSION IDENTIFICATION A SERIES ASSEMBLY CODES I I MI5 3 SPD MAN M20 4 SPD MAN M29 3 SPD AT RZ S3 S4 RZ CS I CD M33 3 SPD AT M38 3 SPD AT KE AJ AN AG TE B SERIES ASSEMBLY CODES M29 3 SPD AT M33 3 SPD AT M38 3 SPD AT CO CY KE AG AJ AN WK F SERIES ASSEMBLY CODES i MI5 3 SPD MAN M20 4 SPD MAN M38 3 SPD AT UR ZM AG WE A I WK AN M21 4 SPD MAN I VI zu I I I H SERIES ASSEMBLY CODES M20 4 SPD MAN M75 5 SPD MAN M29 3 SPD AT I U2 U3 RK RJ CA U6 U7 I M33 3 SPD AT M38 3 SPD AT I KK KL WC I X SERIES ASSEMBLY CODES MI5 3 SPD MAN M20 4 SPD MAN M38 3 SPD AT UR ZM AG WZ AH WL A I T SERIES ASSEMBLY CODES I I MYI 4 SPD MAN MD3 3 SPD AT I DB UA ND I I I GM PARTS DIVISION GENERAL MOTORS CORPORATION CHEVROLET 1D 25 II