Hope you guys can help me i.d. this tranny.

Casting on linkage plate reads:

GM 3831707

Casting on opposite side reads:

3851325
Patent # 3088336

Found a stamping that reads:

GI22I20

Would like to i.d. this tranny as M21 or M22, gear ratios, and production year if possible. If additional info is needed let me know where to look and I'll get it posted. Thanks

 

These may help....http://www.yearone.com/updatedsingle...nfo/muncie.asp
http://www.5speeds.com/muncie2.htm
but the truth is 99% have been rebuilt being as the last were made in the 1970's so it's hard to say what's inside any given case.

Looks like your case is an M20 or M21........
Casting: 3851325 Years: 1964 - 1965 Ratios: M20 2.56 1st , M21 2.20 1st

 

its an M21...also Check the front shaft splines if its ten its a 21

 

??
only real differance between an m20 and m21 are the gear ratios they have the exact same input,output shafts ,cases, tailhousings etc..
the m22 is the same as well with maybe a bigger tail shaft for 400 yoke
and the gears are cut more horizontilly.

 

If it was a stock piece that hadn't ever been rebuilt, what would the ratio's be?
I'm pretty sure it's never been through, as the 427 it came with hasn't. Both are low mileage that have been "shelved" since around '74.

 

I have never seen an M22 with nothing but a 18 or 22 in put spline shaft, M20 and M21 have 10 input spline shaft

 

Yeah .... gear Rhonda will give you the low-down @5speeds.com

 

That casting number is from a mid 60s muncie. How many circular grooves are around the input shaft? No grooves is an m-20 one groove is an m-21.

 

Picts posted:

http://s905.photobucket.com/albums/ac258/sraey8/

 

I always thought it was
no groove = m22
1 groove = m21
2 groove = m20

but after 40 years anything could have been changed inside!!!