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Old 06-16-2019, 02:15 PM   #1
gtdohn
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Default 4 speed to 3 speed swap in a 1948 F1

Can a 3 speed toploader from a 1939 Ford be used in a 1948 f1 pickup with a 6 cylinder flathead. It currently has a 4 speed in it.
Thank you.
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Old 06-16-2019, 03:08 PM   #2
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Default Re: 4 speed to 3 speed swap in a 1948 F1

While anything is possible with a lot of parts changing; the '39 trans is torque tube drive and the F-1 is open drive. Probably easier to start with an open drive truck 3 spd.
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Old 06-16-2019, 04:40 PM   #3
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Default Re: 4 speed to 3 speed swap in a 1948 F1

The 1939 has been converted to open drive. So will it work?
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Old 06-16-2019, 05:26 PM   #4
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Default Re: 4 speed to 3 speed swap in a 1948 F1

If the 6 cylinder already has a 4 speed mated to it, shouldn't it have the half bell required to install the three speed? Just remove the four speed and bolt the three speed in its place. The clutch disc might be different, as well as the drive shaft yoke.
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Old 06-16-2019, 05:26 PM   #5
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Default Re: 4 speed to 3 speed swap in a 1948 F1

The one thing I noticed about the 1939 transmission is that the bell housing is part of the whole transmission, and not a separate piece that can be removed. It is for a V8, so is there no way to use it on a 6 cylinder? Did they make an adapter plate? Or do I have to find a 3 speed that came behind a 6 cylinder from the start?
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Old 06-16-2019, 06:42 PM   #6
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Default Re: 4 speed to 3 speed swap in a 1948 F1

I'm not familiar with the 6 cylinder, so I'm working on assumptions. You should look at your engine/transmission connections now. Is there a "half bell" between your engine and four speed now? It should be a 5-6" housing between the engine and trans.
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Old 06-16-2019, 08:33 PM   #7
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Default Re: 4 speed to 3 speed swap in a 1948 F1

the 39 trans has, we'll call, a half bell housing, which bolts up to the other 1/2 which is on the early blocks. your situation needs the stamped steel 1/2 bell which will fill in the gap between your block, and the 39 trans, as mac stated in your other post. as i also stated in your other post, i have the steel bell for a 6 cyl, its wider than the v8's, i'll never use it, its yours for cheap, i'll never use it, but i do not have the tin starter plate, and dont know if thats a specific plate for that app because the flywheel may be different. call mac, and send me a pm with your thoughts, thanks, skip
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Old 06-16-2019, 11:15 PM   #8
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Default Re: 4 speed to 3 speed swap in a 1948 F1

Thank you Skip. I sent him a PM and asked him if there is a difference in starter plates.
I really appreciate your offer of the bellhousing. I just might take you up on that. If that all works out, I think all I will need is the correct driveshaft and yoke.
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Old 06-17-2019, 09:09 PM   #9
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Default Re: 4 speed to 3 speed swap in a 1948 F1

I can help you with a drive shaft and yoke if you need one give me a p.m.
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Old 06-20-2019, 09:52 AM   #10
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Default Re: 4 speed to 3 speed swap in a 1948 F1

Technically, yes.


4 spd and 3 spd heavy duty are interchangeable. 3 spd light duty is essentially a 39 ford toploader converted to open drive. There is a different driveshaft yoke needed to make it come together if I recall. If your clutch is 11", it should still work with the 3 spd.
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Old 06-20-2019, 10:05 AM   #11
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Default Re: 4 speed to 3 speed swap in a 1948 F1

Quote:
Originally Posted by GreenMonster48 View Post
Technically, yes.


4 spd and 3 spd heavy duty are interchangeable. 3 spd light duty is essentially a 39 ford toploader converted to open drive. There is a different driveshaft yoke needed to make it come together if I recall. If your clutch is 11", it should still work with the 3 spd.
That's what I'm banking on. The clutch, flywheel, and pressure plate are all housed inside the half bellhousing that stays with the motor, so whatever clutch it is will definitely work. The yoke will have to be changed and possibly the drive shaft. I'm sure hoping that's all.
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Old 06-20-2019, 10:09 AM   #12
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Default Re: 4 speed to 3 speed swap in a 1948 F1

Does anyone have a yoke for a 1948 F1 speed open drive? The number for it would be
21C-4841
A correct drive shaft would be great too, but the shipping might be a problem?
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Old 06-20-2019, 12:35 PM   #13
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Default Re: 4 speed to 3 speed swap in a 1948 F1

Contact Scott at B4 Parts in Santa Maria, Ca. He has truck parts.
805 698 8685


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Old 06-20-2019, 05:49 PM   #14
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Default Re: 4 speed to 3 speed swap in a 1948 F1

Thank you.
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Old 06-21-2019, 06:21 AM   #15
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Default Re: 4 speed to 3 speed swap in a 1948 F1

I think the Powerglide yoke from a Chevy is the same part.
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