M-22, M-21 Muncie - Team Camaro Tech
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post #1 of 10 (permalink) Old Nov 23rd, 00, 11:40 AM Thread Starter
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It seams like I have missed something again. I thought all the M-22s had the large main shaft and that this was the only difference between it and the M-21. Now it seems that I was wrong again. Can someone set me straight on this? I need a history lesson on the M-22.

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'69 RS/SS396 pro street
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post #2 of 10 (permalink) Old Nov 23rd, 00, 11:50 AM
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Tell me how's this for confidence : I could be wrong, but I doubt it.
Having owned an original '68 Z/28 with an M22, this is what I know.
The early M22's were 10 splines had NO circular grooves on the input shaft, and output shaft was same size as other muncies. Mine happened to have a fill plug and drain plug in the case. Both plugs were marked "Lisle". Hows that for recalling 20 years ago ? ALL M22's are 2.20 1st. gear close ratio boxes. The large T400 size output shaft and fine 26 spline input shaft started in 1970. Now I'm back into hiding and waiting for the contraversy.

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Rick
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[This message has been edited by YenkoYS100 (edited 11-23-2000).]
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post #3 of 10 (permalink) Old Nov 23rd, 00, 12:40 PM
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http://www.5speeds.com/muncie3.htm

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post #4 of 10 (permalink) Old Nov 23rd, 00, 07:10 PM
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I understand that the gear RATIOS were identical between M-21 and M-22, but that the gears were cut at less of an angle on the M-22 making them stronger, but noisier, hence the nickname "Rock Crusher".

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'69 Garnet Red Convertible, Ivory over black, 350 w/turbo 400
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post #5 of 10 (permalink) Old Nov 23rd, 00, 07:26 PM
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Hi fred, now that you have your answer you better get on over to general tech, were going to start bashing on ya! LOL

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Steve
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post #6 of 10 (permalink) Old Nov 23rd, 00, 11:07 PM Thread Starter
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Thanks for the help. If I got this right,'67 to early '70 M-22 had the small shaft and late '70 to '74 had the large shaft. Did GM replace the Muncie with the super T-10 in '75? I'm sure learning a lot here.
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post #7 of 10 (permalink) Old Nov 24th, 00, 08:54 AM
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3831704 cases (1963) and 3851325 ('64-'65) cases used the 7/8" countershaft, although many have been re-machined and converted to the 1" countershaft which was used from mid-'65 on, starting with the 3885010 case. M-22's were the only 3885010 and 3925660 cases with drain plugs from 1965-70, but starting with the 3925661 case ('70-'74), all Muncies had drain plugs.

More M-22 trivia; a fine-spline (26 tooth) input shaft does NOT necessarily signify an M-22. There were seven different Muncie input shafts - all 26-spline inputs had 32-spline outputs, and all 10-spline inputs had 27-spline outputs.

This refers to original build specs - not many Muncies are still around that haven't been rebuilt at least once, and due to the high degree of interchangeability of the cases and internal parts across the years and models, it's possible to build almost any combination from parts (which rebuilders have lots of).

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JohnZ
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post #8 of 10 (permalink) Old Nov 29th, 00, 07:56 AM
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I keep hearing what you said about the drain
plug issue BUT I have a 69Z with the original M20 that has a drain plug It is the 660 casting..... it still has the original rpoZ28 tag attached to the cover bolts with the Nos. 3946797
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post #9 of 10 (permalink) Old Nov 29th, 00, 08:20 AM
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And to further obfuscate the issue, many Muncies are Frankensteined. to wit, I have a 65 M21 with a post 69 side cover. ?? No wonder I couldn't figure it out?
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post #10 of 10 (permalink) Old Dec 1st, 00, 10:24 AM
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Z-Man -

The metal tag on your cover bolt is correct for your M20 (my untouched '69 M21 has the tag with 3946798 on it); both are the correct original released transmission part numbers as shown in the A.I.M. I wish mine had a drain plug - someone at Muncie must have grabbed a case intended for an M22 when they assembled yours and nobody noticed, or someone drilled and tapped it later (as I have done on several Muncies for earlier projects). Be glad you have the drain plug!

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