Automatic Transmission Diagnosis - 4L60-E: Identification: Transmission
The Hydra-Matic 4L60-E automatic transmission can be identified by a letter code contained in identification number. Identification number is stamped on transmission case above oil pan rail on right rear side, or to rear of oil pan. See Fig 1. Identification number contains information which must be used when ordering replacement parts. Transmission RPO code is M32 on Sierra models with 6.0L engine and M30 on all other models.