Section 102 (Automatic Transmission Diagnosis - 4L60-E): Identification: Transmission
WARNING: This page does not describe the selected car, but rather 36 other vehicles, including the 2002 Pontiac Firebird, 2002 Oldsmobile Bravada, 2002 GMC Yukon XL, 2002 GMC Yukon, and 2002 GMC Sonoma. However, it is still accessible from the selected car via links, so may be relevant.
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.