Re: munsie question
396SS... I believe you are correct. I too have a 3885010, but neglected to look for grooves on the shaft when replacing the clutch ( think I have M21 ). That casing appears to have been used for M20/21/22 . I believe the grooves on the shaft were for identifying the trans on the assembly line...
Year 1962-1965 Type: M20 Rings: None Ratio: 2.56 / 1.91 / 1.48 / 1.00
Year 1966-1974 Type: M20 Rings: Two Ratio: 2.52 / 1.88 / 1.46 / 1.00
Year 1963-1974 Type: M21 Rings: One Ratio: 2.20 / 1.64 / 1.28 / 1.00
Year 1967-1974 Type: M22 Rings: None Ratio: 2.20 / 1.64 / 1.28 / 1.00