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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!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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For helping keep this great
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| | | | Joined: Oct 2016 Posts: 14 Wrench Fetcher | | Wrench Fetcher Joined: Oct 2016 Posts: 14 | What is the model or designation for the four speed non syncro 4 speed used prior to the SM420? Would like to find gaskets, seals etc. Thanks in advance | | | | | Joined: Oct 2013 Posts: 331 Shop Shark | | Shop Shark Joined: Oct 2013 Posts: 331 | There isn't one. It's just a GM 4-speed, used from '31 to '47 in trucks and school buses only I believe. It's a non-sychronized crash box with straight cut gears. It was the predecessor to the SM420. Here's a link to a drawing of it: http://chevy.oldcarmanualproject.com/parts/1929_54/221.htmShould have casting number "GM 590474" on the left side of the case.
1950 4100 - unrestored and driven weekly for almost no reason at all.
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | The Filling Station list a gasket set for the 1931 to 47 4 speed transmission as G-7023 for 26.50. | | | | | Joined: Jul 2014 Posts: 21 New Guy | | New Guy Joined: Jul 2014 Posts: 21 | Is this going to be the same for my 1941 GMC 2.5 ton vs Chevy?
Brad | | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | That early transmission can be identified by the reverse lock-out lever on the shifter.
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