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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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#16829 08/21/2004 10:47 PM | Joined: Mar 2002 Posts: 553 Shop Shark | | Shop Shark Joined: Mar 2002 Posts: 553 | I have original drive train equipment on my 1945 half ton. I want to eventually convert to an open driveline, but I'd like to keep the straight six. I have this extra transmission below. Everything looks identical except that it has a open driveline setup on the yoke. There's some casting nunbers on the left side, 590474. Will this fit on my bell housing and into the clutch disc? [img] http://img.villagephotos.com/p/2003-9/378428/tranny_590474.JPG[/img] | | |
#16830 08/22/2004 1:04 AM | Joined: Nov 2001 Posts: 481 Shop Shark | | Shop Shark Joined: Nov 2001 Posts: 481 | Hi John
I've thought about that conversion myself but I haven't tried it yet so I don't know for sure.
I think that trans will bolt right in. It even measures like you can bolt up your stock 1/2 ton brake and clutch pedals. I also think the rear end of that trans will bolt on to a 1/2 ton 4 speed in place of the torque tube. | | |
#16831 08/22/2004 1:24 AM | Joined: Jun 2004 Posts: 336 Member | | Member Joined: Jun 2004 Posts: 336 | What you have there is a SM420. I had a torque tube (closed driveline) in my 54 with a SM420. I got a SM420 out of a 1967 truck and it bolted right in place of the old one. The two transmissions were identical exept the later model had the yoke like your pix. Bonus: the 67 has a switch for backup light(s). The next trick is getting a new driveshaft. The new driveshaft needed to be just over 64" with a slip joint. I couldn't find a one piece 'shaft that would work. The guy at the local driveshaft shop told me long ones were really hard to find and he suggested that I bite the bullet and get a two piece 'shaft. That's what I did, so I had to make a mount for a steady bearing... The good news is that I have a modern posi rearend and have lots of gear ratio choices!
Logically, if the transmission in your 45 is compatible with the 54 (I don't know if it is), then the trans in your picture should work.
Gord
1954 1/2 ton 235 4 speed
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#16832 08/22/2004 2:48 AM | Joined: Nov 2001 Posts: 481 Shop Shark | | Shop Shark Joined: Nov 2001 Posts: 481 | I don't think that's an SM420. The cover on the top of the trans is different than the 420 and it has a lockout lever for reverse.
I believe these were used at least 41-46 on 1 ton and larger conventional cabs. | | |
#16833 08/22/2004 3:38 PM | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | That looks like the old style 4 speed with the
trigger lock out for reverse. It will probably
fit but there not good for much. It,s a crash
box with no syncro,s.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | |
#16834 08/22/2004 4:05 PM | Joined: Jun 2004 Posts: 336 Member | | Member Joined: Jun 2004 Posts: 336 | Yes Rusty, I screwed up. The side cover plate and rear housing looks like the SM420, but the top looks too tall. Besides, I think the SM420 came out in 1947 - this looks earlier.
There's still a lot of messing around to convert to open driveshaft. If you are going to take on the project, start with a good transmission.
Gord
1954 1/2 ton 235 4 speed
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#16835 08/22/2004 7:48 PM | Joined: Mar 2002 Posts: 553 Shop Shark | | Shop Shark Joined: Mar 2002 Posts: 553 | Okay, thanks for the info. I guess that tranny is a dud. Maybe I'll rebuild my existing one instead. Is rebuilding a transmission hard to do? :rolleyes: | | |
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