The Stovebolt Site Forums The Shop Area Driveline 54 Chev SM 420 Swap

I have a stock 54 chev 3100 truck with an SM 420 trans serial number 591465 which puts it in the 47-53 range. I bought an SM420 serial number 3830574 which puts it in the 64-67 range. It has a 10spline output. I want to know if i can convert the newer one to fit up with the torque tube u-joints on the old trans or do I need one of the correct vintage. It appears its doable. Any help would be appreciated.

Look at Engine Compatibility & Adaptability.

I think you can use your enclosed driveshaft rear cover. Wait to hear from other people.

I do not know about the u-joint yokes (especially on the transmission side).

Yes, I have studied this as of recently, you can use the rear bearing cover (including speedometer drive and driven gear) of yours and install it on the later trans with your yoke, u-joint and torque tube adapter and you will be just fine.

I have 2 sm420 in my garage apart rebuilding them , one a 54 and the other a 60s and they are the same.

I hope you, or someone sees this, and can reply. I have a sm420, #591953 with a worn out driven gear. Are there after market replacements? Can I adapt a bullet to this tranny?

Thanks for any help or pointing me in the right direction.

Don

Don,

Novak transmissions, at the link I gave above, probably has/sells the part you want.
You might find it listed by part number on eBay.
You might want to post a part-wanted ad here.

“Can I adapt a bullet to this tranny.”
What is a bullet?
If it is the enclosed drive-shaft enclosure/fittings, yes (for/on any SM 420 transmission).
You would also need both of the enclosed drive-shaft 4-speed u-joint yokes.

Occasionally you will find drive and driven gears for the sm420 on ebay. Make sure you match the pitch, both drive and driven gears must have the same pitch or they will eat each other. Tell me your what you have/need and I will look through my parts.
Steve