Thread: are SC and nonSC trans the same

i have an 06 GT not comp g. im trying to find a transmission but every tranny i find is for the nonSC... are they the same? and will the 05 and 04 trans work? also someone told me about a trans 4 speed 4t65e m15 gm option code f83 3.05 ratio....

what is the m15?
what is the gm code f83?
and whats the difference in all the other trannys and the 3.05 ratio?

Originally Posted by Trannyman95

The best way to replace what you have now is with a trans with the same ID code on it. The SC and non-SC transmissions do have a few changes and are not a direct swap. The SC transmissions, aside the CompG version which I dont know was available in 06, have a different gear ratio that will cause problems if exchanges with a non-SC trans. The SC transmissions have a 2.93 ratio, Tapshift CompG has a 3.29 ratio, and the GXP transmissions have a 2.93 ratio though the bellhousing is different and wont work out anyways. Internally they are the same except for the drive/driven chain sprocket ratio. The SC/HD transmissions use a larger differential that uses a specific matching passanger side axle that wont fit in a non-SC transmission. If the transmission is being rebuilt it is easy to mix and match parts, but to swap one out for another is going to come with a few problems. The gear ratio is something that can be tuned to change also if need be.

Trannyman, isn't there some kind of transaxle casting number "stamped" on the bell housing, that is "supposed" to correspond to either a 4T65E M15 (non-HD) or a 4T65E MN7 (HD) transaxle? Please correct me, either way because, I just cannot remember what they both are. I thought I read it here at grandprixforum.net?

Seems like M15 (non-HD) is a big "923", but is this reversed?

OR could you remind me what both are again, please?

Thanks for reading.

Robert.McArdle@Comcast.net

Originally Posted by Trannyman95

The casting numbers mean nothing to me, you HAVE to go by the ID tag information or there is no way to tell. The cases for the most part all interchange with each other and is not an identifier of what the internal build of the transmission is. M15 is a standard 4T65E, MN7 is the HD version which has the larger differential with matching output shaft and tail housing.

Thanks for the quick reply. Let me see if I have this straight. So, they are shells, with casting numbers that indicate the "original internal build" (M15 or MN7), only? But will never guaranty "integrety" of the MN7 (Gear ratio 2.93/sprockets, Diff-HD, and front Passenger side drive axle) are still present? And Vise/ Versa? If still correct, and that being said, can I know, if the "casting (only)" started out as an MN7 or M15?