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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Jun 2023 Posts: 25 'Bolter | | 'Bolter Joined: Jun 2023 Posts: 25 | Howdy! I have a 1954 3100, 3 speed, torque tube driveline. For sundry reasons I would like to convert to the SM420 transmission, which was an option originally for that truck. Herein lies my question: if I find a tranny made post 1955 for an open driveline truck, can it still be made to work with my torque tube rear? I have heard that the tailhousing from my 3 speed (the piece that bolts to the driveline) is interchangeable with the SM420; does anyone have the experience to say this is true?
Thanks!
-Curtis | | | | | Joined: Mar 2004 Posts: 6,233 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,233 | They are not the same, you need the SM420 Bearing Retainer with casting number 591679 to convert a newer open drive shaft trans to the 1954 and back closed dive shaft. There are a couple on ePay now, just search "591679 bearing retainer". Mike B  | | | | | Joined: Jun 2023 Posts: 25 'Bolter | | 'Bolter Joined: Jun 2023 Posts: 25 | Awesome, thanks for the info! | | | | | Joined: Nov 2021 Posts: 1,403 'Bolter | | 'Bolter Joined: Nov 2021 Posts: 1,403 | Not close to you but I do have a 4 speed I removed from my '50 3600 that has a torque tube back end (the 3600 had an eclosed front drive shaft and an open rear drive shaft). I can not atest to the transmissions condition as it was removed early in my restoration. PM me if you are interested. | | | | | Joined: Feb 2004 Posts: 29,875 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,875 | The hard to find part for that conversion is the universal joint. They're very scarce, and usually expensive if you manage to locate one for sale.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Dec 2019 Posts: 446 'Bolter | | 'Bolter Joined: Dec 2019 Posts: 446 | Why make it hard? there should be plenty of torque tube sm420's out there. I support the KISS theory. LOL I guess my question is, why? the only gain is a granny, unless you are using your AD as a farm/work truck.
Larry
Old man᠁Old truck᠁neither one goes very fast. All you need in life is TIME, PATIENCE and MONEY.
If you are missing one component, you'll need an abundance of the others two.
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