['ol Pinion head]

....1/2", For some reason the '70 GTO's with the 455 got there own code of Muncie, code WG, I believe. Have had two of these '70 factory 455 4speed GTO's, both with A/C, & both had lunched their original Muncies & been swapped out, so I can't say what was different with them from the M21's used behind close ratio equipped GTO's that year. This is a question I have wondered about for years. The 455 version may have been Pontiac's first use of the big output shaft fine spline input Muncie.

The big output shaft Muncies were 1st released in the '70 GM model year in LS6 & L78 Chevelles from all the all the # decyphering I have done on Muncies during the rebuilding process. Probably also used in the highest horse Vettes this year. For some reason, I believe they were not used in the '70 high horse L78 Nova's & Camaro's, instead they used small output shaft versions. The '70 T/A, I believe also used the small output shaft Muncie too.

For 1971 models, All Muncies used by all 4 divisions had the big output shaft & fine spline inputs. These were available in all 3 versions: wide ratio M20, close ratio M21, & M22(HD close ratio-rockcrusher). The 455 HO cars optioned with a 4 speed got the M22. Originally for '71, the 3.90 8.2 10 bolt gear set was planned for certain no a/c 400 4speed (close ratio) A-bodies. Believe this was a M21 not a M22. A very few early '71 A-bodies were even delivered 3.90's & M21's. The vast majority of these 400 4 speed cars had M20's & 3.55's or 3.23's.

For '72, the M22's continued behind the 455HO 4speed cars. I believe, as low ratioed as one could get behind a 400 Pontiac 4bbl A-body, was a 3.55 (3.23 with a/c), so I believe, no M21's. The '72 M21's I have built or bought came out of '72 Camaro's & Vettes.

For '73 the M22 was gone in the Pontiac line. If GM still used it was in a high horse (for '73, lol) BB Vette application. Don't know enough about the no a/c 4speed SD T/A's to say M-21 or M20. Do know, my '73 4speed A/C 455 D-port T/A has its original M20 & 3.42's. These big ouput shaft Muncies were used up until mid '74 & the '74 version's side covers will have 2 bosses for TCS switches.

Better stop, please excuse the length of this minature novel.

[This message has been edited by 'ol Pinion head (edited 10-26-2000).]

[This message has been edited by 'ol Pinion head (edited 10-27-2000).]