The Stovebolt Site Forums The Shop Area Driveline Sm 420

I hope this information helps someone.

I transferred a 1954 sm 420 into my 48 1/2 ton chevy. I like a floor shift and it works fine. But, I wanted a backup lamp for safety and found a 67 sm 420 lid. It fits fine but will slip out of 3rd. I called Novak for help and advice. They said the shift forks are different and I need to switch the 3/4 forks from my 54 lid into the 67 lid inorder for it to work correctly. Their rebuild kits are different for the various years. Kits come for years 47-53, 54-63, and 64-67.

Good information to know.... Thanks John

not to step no your,but how do you identify thesm420?ihave a granny box out of 1966.i lust do,nt kknow what iam looking for.thanks for your info.

Novak has a list of how to id and how to modify if needed.
http://www.novak-adapt.com/knowledge/sm420.htm
Easy read and a phone number for questions. Good as I could find.

I have had trouble with third gears on my M420,s. I believe they wear out because they get used the most. I suspect that either the nshaft of the bushing wear because of the stress of downshifting. So my question is does anyone know the specs on the mainshaft and the bushing that the gear rides on?

I am on the verge of the second time around with the third gear noise. Granted both were old and used when I started, but I want to really fix it this time.

I plan on getting a rebuild kit and some extras to make sure everything is up to standards.