TRANSMISSION IDENTIFICATION INCLUDING AXLE RATIO TRANSMISSION TO ASSEMBLY CODES Note Transmission identification can be located in one of three positions on the transmission A Identification plate on side of case B Stamping number on governor cover C Ink stamped on bell housing 1985 M39 5 SPD MAN MD8 3 SPD A T MB1 5 SPD MAN THM7OOR4 5DT PO Y8 YZ YX 5DU YP ML3 5 SPD MAN NW 1986 MD8 4 SPD A T THMTOOR4 M39 5 SPD MAN MB1 5 SPD MAN GPL 6YF 6YP GYX DT DU 6YZ 6YS 6YW MC4 SPORT SHIFT ML3 5 SPD MAN NO CODES AVAILABLE NO CODES AVAILABLE 1987 MD8 4 SPD A T THMTOOR4 M39 5 SPD MAN MB1 5 SPD MAN 7YFM 7YSM 7YXM 7YMM UUR ZZC UUP 7YPM 7YWM 7YZM 1988 MD8 4 SPD A T THMTOOR4 M39 5 SPD MAN MB1 5 SPD MAN BYXM 8YPM 8YZM 8YWM NO CODES AVAILABLE NO CODES AVAILABLE 8YMM MK6 5 SPD MAN NO CODES AVAILABLE t 1988 GENERAL MOTORS SERVICE PARTS OPERATIONS CHEVROLET 17E REV 6 88 43