The SM 420 4 speed trans . 1955 to 1966

uses the SECOND DESIGN counter shaft .

http://i669.photobucket.com/albums/...ond%20design_GM_3813197__zps6izwqfgb.jpg

The second design is mounted with ONE bolt at the rear.

The groove on the counter shaft uses a snap ring / circlip which holds the rear

bearing in place .

I'm assuming this is the snap ring you need ?

This snap ring I have in mind MEASURES ( .050 " ) thick .

You should carefully measure the WIDTH of the groove on your counter shaft .

If the groove measures right around ( .050 " ) width .

I would be 99% certain that the GM part you would need is......

GM # 4.422 - GM # 591959


Availability of GM # 591959


Friesen Chevrolet
Sutton, Nebraska
phone: 402 -773 - 5538

Friesen has ( 14 ) GM # 591959 in stock


Dan's GM Obsolete
Chinook, Montana
phone: 406 - 357 - 2615

Dan's has ( 14 ) GM # 591959 in stock


Howe Motors
Claremont, N.H.
phone: 603 - 542 - 5181

Howe Motors has ( 4 ) GM # 591959 in stock


see PIC below

not a great PIC........but better then no pic


http://i669.photobucket.com/albums/...Ring_SM_420_1955_and_up__zpsporgsmuu.jpg



You will also need a new front of the case counter shaft Cover / Spacer


http://i669.photobucket.com/albums/...M%20420%20COVER%20SPACER_zpsldrcszue.jpg


Dan's Obsolete has ( 10 ) GM # 3795505 in stock


George
'54 3600






Last edited by '54 3600; 12/25/2017 1:02 PM. Reason: add photo
1954 3600
A big help to many on the Bolt
Now cruising in
The Passing Lane