Quote Originally Posted by Trannyman95 View Post
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?