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7 Posts
Discussion Starter #1
I’m researching my transmission and need help. Trying to find out exactly what I have. Listed below are all the items I have researched so far however they may incorrect. Any help would be appreciated.
P9R21A build date -
P=Muncie Plant
21=21 day
A=muncie 20 wide trans.
GM3846429=1963-65 Pontiac long tailshaft
3952648=side cover casting no.
3925660=1968-1970 GM Casting Number (I found reference that all documented M22 trans. Have this number
Trans. Patent number=3088668 I can find no information on this number
On very top of the trans is ID Number. 16K33P388 - I can find no information on this number. The number does NOT match the VIN number on my car.
Is there any additional numbers I should be looking for?
As you can see I need some help or point me in the right direction. Thank you.

4,387 Posts
Appears to be a Chevy.

1= Chevrolet Division
6 = 1966
K = Leeds Assembly plant, Kansas City which produced Chevelle's and El Camino.

Tailhousing number is not for a long tailshaft, and it would have to have been fitted to the car and very noticeable in its length.

Your tailshaft shows to be 1964-'65 which would be fitting for a 1966 transmission.

1,008 Posts
my 70 m22 has a 660 case .... its never been apart ...
660's are 68-70 ....
my 68 m20 is a 660 also

that side cover should have the tcs switch on 3-4 fairly sure that started in 70
maybe california cars in 69 ... maybe ...
I have that cover on a 71 wide ratio
that side cover uses a bolt to hold the levers like the 69

that "thin fin " tail shaft is on my 68 wide ratio w drivers side speedo I think they used em a little later than 65 66 also they should have a "winters" casting mark on em for the year it was cast also

your right
somethins not jivin' it should not start with a 1
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