Transmission Questions

Hey guys I have a couple questions for you. I have a 2001 grand prix gt. On the bottom of the transmission pan the stamp says "M6". I know the M15 is the 4t-65e non HD version and the MN7 is the HD version of the 4t-65e. Can anyone tell me what the M6 is or if its just another way gm coded the 4t65e. thanks a lot.

There is a little history on the GM 4T65E tranny. There were two designs on the tranny oil pan (1st design and 2nd design).

The M6 stamped on the tranny pan has nothing to do with GM RPO codes. Since you have a GT with a regular 4T65E the RPO code is M15. From circa 1999 and up all Grand Prixs have the 2nd design tranny oil pan.

What the M6 means is you have the oil pan and 4T65E tranny that uses the M6 bolt size. There are two different production sizes on the bolts and machining........M6 or M8. There are a total of 20 bolts.

1st design
M8 X 1.25 X 18

2nd design
M6 X 1.0 X 17

hey thanks a lot bnaylor i appericate the info. kinda feel like an idiot now lol. i was told that the code was stamped on the tranny pan so i was curious. thanks for the clarification.

hey thanks a lot bnaylor i appericate the info. kinda feel like an idiot now lol. i was told that the code was stamped on the tranny pan so i was curious. thanks for the clarification.

You're welcome. There are two ways to tell what tranny you have either via the VIN number and a source that can provide the info or by the SPID label located on the back of the trunk lid or spare tire cover which lists all RPO codes and options your Grand Prix has. Just look for M15 on one of the data lines which means the regular 4T65E tranny. Your engine code is L36. The paint and trim code is the last line of data.