Transmission change in 1950 F1 Question

[oneoldtruckguy]

I have a 1950 Ford F1 with a original Flathead V-8 and a Non Syn 4-speed tranny. I just bought a Real Nice 3-speed out of a 1940 Ford pickup and am having it gone thru at the transmission shop right now. My question is what do I have to do and What else do I need to take the 4-speed out and install the 3-speed. Will it hook right up or do I need other parts???? Also does the 1940 3-speed and the 1950 4-speed take the same clutch????
Thanks For the Help!

[Vanspeed]

You need the correct 3 spd. driveshaft. I put a 3 spd. in my 48 and I left the 11 inch clutch in place. I didn't notice a difference in the trans mount.

[oneoldtruckguy]

Do You know what size drive shaft?

[Rowdy]

The 40 transmission likely still has the rear bearing retainer for a closed drive shaft. You will need the 42 and later pickup rear bearing retainer with the speedometer drive built into it for the open drive shaft, transmission output shaft along with the drive shaft mentioned already. Rod

[Ross F-1]

The stock 3-sp driveshaft is right about 62.75" from center-to-center on the u-joint cups. I don't know the diameter off hand.

I'd guess if your truck had a 4-sp that it also has the 4.27 rear axle? Before you get a driveshaft made, you should decide whether you want to live with that or change it to something better. A stock 48-50 F-1 Dana 41 came with 3.73 gears, which is really quite good if you have to deal with hills and high altitude.

[Barry-ct]

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The stock rears were 3.92 or 4.27 for 48-52.

[Ross F-1]

From 48-50, 3.73 was standard, 4.27 and a 3.92 ratio was available. The 3.92 was a different tooth count than used in 51-52's with a 3.92.

Actually there was some discussion to the effect that the later 3.92 came in midway thru '50, when the bedsides were changed to flat.

[oneoldtruckguy]

How do I tell what rear end gear I have???
Thanks Guys!

[GreenMonster48]

There should hopefully be a tag on the rearend with numbers as seem in Ross' picture. Like if your tag says 41/11, that does NOT indicate a 4.11:1 as I thought, but you divide the two numbers.

41/11= 3.727 (3.73)

[rotorwrench]

The Dana 41 has a rear cover that is almost round where the later Dana 44 has a shape that has flats on both sides. There was generally a tag with the tooth count attached with one of the cover bolts as mentioned before. The Dana 41 had the 3.91:1 ratio gears for the Mercs with overdrive but the F1 with the light duty generally had the 3.73:1 unless is has a 4-speed. The later Dana 44 had the 3.92:1 gears with different tooth count but very close to the same ratio as the 3.91:1 Dana 41. The stump puller 4-speed generally dates back into the 40s and is not synchronized like the 3-speed. There are some later 4-speeds that are better and have synchronizers but they didn't come along in the early F1 days and you don't find them as often.

There were some F1 pickups that came with the 10-inch Long type clutch but they are rare. The 11-inch will work or you can have any 8BA flywheel drilled for the 10-inch Long type clutch. A 49 thru early 51 Merc Borg & Beck clutch will work also since they still had the 1 3/8" 10-spline input configuration. There should be more than a few F1 light duty 3-speed driveshafts out there but you will have to search the salvage yards & maybe flea-pay to find one. Put a want add in the swap meet section. Someone may have one.

[Mike B]

Re: the drive shaft, '42-'47 PU's with the 3 speed are the same as well.

I'm using a shaft from a '50 F1 in my '42...no mod's required.

I have the end pieces and yoke if you can't find one, IIRC, the shaft is 3.5inches in diameter.

[Ross F-1]

48-52 F-1's with light duty 3-sp came with 10" Long clutches. With the HD 3-sp or the crashbox you got the 11".

[scooder]

Helicopter bloke, I have a Dana 41 from an overdrive Merc and also Dana 44. They are both 4.27:1. I thunk 3.91 was standard 3 speed trans?
Martin.

[rotorwrench]

Both of my 51 Mercs have overdrive and they are both 3.92:1 Dana 44 types. The parts catalog for the Mercs lists a tidbit of info when you check the complete axle listings. For the 1949 & 50 it has dots & stars to designate purpose for the axles. The 8M-4006-A has a star (3.91:1) and the suffix B(4.27:1) & C(4.55:1) units have a dot. In the legend at the bottom of the page the star is stated for use as standard equipment and with overdrive in flat country and the dot is stated for standard equipment and overdrive in mountainous country. None of them were used with Merc-O-Matic.

My manual (with blue cover) is dated November 1950 and is for the beginning 1951 model year back to 1949.

[scooder]

Cool info, thanks. Mine were from them thar hills, I guess.
Martin.