Transmission advice

tamnalan

tamnalan

Senior Member
I'm the proud new owner of a '39 Ford pickup. I recently hauled it back home:
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I'm not sure if the motor is original:

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It has a 4-speed trans with the straight cut gears. I want to rebuild this truck to be as original as possible but also suitable daily driving and for longer distance trips at typical road speeds today. What should I do? I hear the T5 is a nice swap.

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Hi there, Nice original pickup. I learnt to drive in one of those. Nice to keep it original but in doing so you could not expect it to do highway speeds of 60 to 70 mph plus, they just wernt built or geared for that kind of driving. If you hop it up, change transmissions and rear end gearing it wont be as Henry built it anymore. Good luck with it. Regards, Kevin.
 
My 47 is still fairly original and my daily driver. We left the 4spd in and swapped out rear diff for a 2004 f150 we shortened 12" this gave a nice gear and disc brakes. That 8.8 bolted up to my original drive shaft also. Is your truck bigger than half ton. I bought a 39 3/4 ton last year waiting till my wife's 41 is finished
 
The VIN is 18-4733621. I think it's a model 91C. The 4-speed's bellhousing flange is unstamped.
This truck came from a field near my hometown in central Montana. The US Army trained B-17 pilots there during WWII. The 615 Bomb Squadron was the last unit to train (in 1943), and so I'm planning to mark this truck as an Army purchase for that squadron (OD color, their squadron symbol, NDT tires, lunette hitch on the back.) I will leave the 6 volt system, interior, and engine all stock.

Will the '39 standard three speed enable 55-60 mph cruise speeds? That would be enough.
 
I restored a 1943 Willys MB a few years ago. Here's a pic of it and a camper trailer I built. The Willys is just too slow to safely drive it on most roads unless I'm in a convoy with others. Plus the open cab, hand wipers, and lack of heat make it a little uncomfortable on long trips.

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I had a 4 - speed crash box in my '37. With 3.78 rear end, it would do 65 - 70 all day long. ****** doesn't affect cruising speed. Fourth gear is same as 3 - speed: 1:1. Really boils down to whether you want to futz with double clutching. The 4 - speeds make the sweetest sounds!
 
tamnalan said:
Would you buy/build another vehicle with a crash box?
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I like them a lot!! I drove a 1941 GMC tow truck when I was 16 years old, some WW2 trucks in Kaui in 1966, a 3 axle truck with a 5 speed and a three speed browning (15 speeds) in the 1970's...
Can't loan it out though, and the wife can't drive it...

Karl
 
Is your truck a 1/2 or 3/4 ton? If it is 1/2 ton, I would consider using a passenger car/light commercial three speed transmission with '39-'48 gears, and 3.78 gears in the banjo rear. You can hang on to the parts you remove in case you or the next owner wishes to go back to original.That would allow you to run all day at 55-65 mph. You really don't need to go 70-75 mph IMHO.
 
I appreciate all the comments!

How would I tell if it's a 3/4 ton?

It has a 112" wheel base. Are the 3/4 ton trucks all 122", with a bigger box?
 
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Less hassle and more pleasant to drive with '39 three speed. Shifting less stressful than the crashbox. I not a fan of all the double clutching. As for your highway speeds you really don't want to take it over 55 or 60 without other mods to frame and suspension for safety. Not knowing what your rear gears are hard to talk about a comfortable cruising speed but I had a 4:11 in my '35 and went with 7.50 tires, ( tallest that I could comfortably fit ) and that gave me a comfortable RPM at 60.
Looks like a great find, good luck and have fun.
 
I replaced a four-speed crash box in my F-1 with a regular 3-speed. Dramatic improvement in drivability!! You should be able to put in a regular '39 car ****** without any trouble.
 
I've put many miles on my crash box and don't mind double clutch and the gear wine. Kinda the feel and sound of my 1 ton should have
 
tamnalan said:
I appreciate all the comments!

How would I tell if it's a 3/4 ton?

It has a 112" wheel base. Are the 3/4 ton trucks all 122", with a bigger box?
Click to expand...

I had a '39 3/4 ton PU several years ago. It had a heavier duty suspension and the differential was not a banjo type rear but instead it had a heavier duty truck type rear like you would find on a 1 ton or larger truck. There are probably other ways of telling a 1/2 from a 3/4 ton.
 
nice looking truck, 4 spd is a bear to drive in any traffic and around town, put a 3 spd syncro trans out of 39 up car if you can, it has a higher first/second gear ratio's and does better, use a 3:78 rear end from a car, bolts right up, easy swap and plentiful if you ask around, probably a buch of hot rodders around and with the modern engine swaps they do away with these parts, trans can run from $150 up, rear axles complete $100- look for the numbers stamped in the bottom of rear end at the torgue tube 9-34 is 3:78 ratio-check yours it may have already been changed--good luck and keep us informed, ask questions this is a great forum to get answers
 
It appears to be a 1/2-ton. As was mentioned the 3/4-ton was a longer frame (122" WB) and different rear axle (not banjo style). The old 4-speeds were used at least up to 1952. I would rather have a 3 speed light duty myself. I double clutched for many moons with my Dad's old 52 F3 but it got old after a while. It was great when hauling a big irrigation engine, water tank, or a bull but not so great for everyday type driving.

A fellow modified a 49 to early 51 Mercury car transmission with electric overdrive to use a top shifter from an old four speed truck box and it looked like it worked pretty well in a later 40s model 1/2-ton. Just a thought but it can be done if you put your mind to it. There are photos on here somewhere of that rig.
 
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