Technical 1939 Ford Coupe – Options to Add Overdrive

Hey everyone,

Posting on behalf of a friend who recently purchased a 1939 Ford that's all original – flathead, 3-speed in the floor, stock rear end, and stock wheels. He’s looking to add overdrive to help the car cruise more comfortably on the highway since he wants to take it to events that are several hours away.

Is there a transmission or overdrive unit that can be added to the existing driveline? Any suggestions or ideas would be much appreciated. Thanks!

 

This one’s sold, but it’s a start for the traditional solution.

https://www.jalopyjournal.com/forum/threads/columbia-two-speed-rear-end-1940-ford.1286424/

 

Just something to think about. I
Was thinking about doing the same thing in my 41 Ford coupe as it has 3.70 gears in the Rear end so 60 miles an hour It's about 3000 rpm. On a flat road it would be nice to have the extra gear but just about any incline.I wouldn't have the power to pull it. The motor in my car is a stock rebuilt 8 CM motor. Perhaps if you've got a little bit more power an overdrive would be nice. But I
Believe the overdrive cars had a lower rear end ratio to start with so that the overdrive wasn't such a drop.

 

Had a Michell in a Model A and it worked well. Can be lever or cable shifted.

https://mitchelloverdrives.com/products/ford-v-8-overdrive/

 

Neither is inexpensive, I would go with the Mitchell. Modern components, works well. Relitivly easy install.

 

I installed mine alone except for my neighbor helping with plugging the driveshaft into the u-joint.

 

This answer won’t suit everybody but it’s a cheaper option: I recently built a ‘51 F-1 and the owners didn’t want to add an overdrive etc. I put in a 3.08 diff and the flathead pulls it no problem. The other best option in my opinion is to go to a T5 5 speed. The kit’s are available to do it and since all 5 gears have synchro’s it’s much more pleasant to drive. Krylon 32 here sells some adapters and I have bought a couple kit’s from John Baker at Transmission Exchange in Kentucky (the kit’s I bought were for a model A but he may do the later ones as well)

 

The easy ways to keep it stock (read not cheap) is to either find a complete Columbia rear end or change the gear set to 3.54/3.25.

 

This statement doesn't seem right. I would start by checking the tune on your engine.

 

The tune is good tubman.i should have said the inclines around here get me down to 45mph near the top in 3rd so od wouldn't help on t hat.

 

Thanks for all the great feedback! I will pass this information on to see what direction he would like to go.

Respectfully,

Fityfive

 

I have had flathead (usually stronger than stock but still very street worthy) powered cars for well over 50 years. My personal recommendation is a t 5–5 spd hooked up with a replaceable pumpkin(as in a 8 or 9 in Ford). The t 5 can come from a variety of vehicles and most have an o/d ratio around .078 or close to that number. I had a 32 cabriolet highboy that was equipped with a t 5 and a 2.75 gear and 70 mph was only 1900—granted this was a 250 in flatmotor that dynoed out approximately 150 h.p.; when I would take it to the track,changed out the pumpkin and ran a 3:89 gear that helped to push the lightweight car(no fenders,no hood)to 80 mph in the 1/8 mile. All of this with a light aluminum flywheel(get one that has a bronze or steel insert) and a 9 in clutch and pressure plate. Some people run an 11 in clutch(not needed just extra weight to pull the motor down).A 8 in Ford rear out of a 60’s. Falcon,Mustang,Maverick is plenty strong enuf to support all the power even with a very strong flathead. Get rid of those old Ford three speeds and banjo rear ends. They were marginal when new and now even weaker after 60-70-80 years of use and abuse!!

 

@CTaulbert builds a closed drive T5 for just such an occasion. If you really want to go for it.

I think unless your running 80+ mph that I’d put some 750:16’s on the back and let it rip. Tons and tons of people driving flat head/ 3 speed/ banjo cars 70 mph all day. I’ve seen @flatout51 run his roadster 80+ for 3 or 4 hours straight no trouble

 

I had a " MITCHELL " overdrive in my 1947 Ford Coupe, it worked great. It was a cable system.

 

The modified T5 for closed drive is a good solution; I would look at the Mitchel. It's cost is about $3000, however, you really have a 6 speed set up because you can 'split" shift. You can go into 2nd gear overdrive if you need to to pull a steep hill. Also, you can put the mitchel in neutral, put the trans in first, then move the mitchel into low range. I understand the model A guys do this so they don't have to completely stop to get into first gear. I seriously considered the Mitchel for my '41 p/u, but with all the frame work needed, I went with a different transmission.

 

Fiiirst gear - quick into Secoooond geeeear - now into thiiiiiiiiiirrrrrrrrrrrrrrrrrddddd and getting on the higwaaaaaaaaayy --- oh shit it's 65 and Im topped out... (hits columbia switch and lets out clutch) ....... Ahh. Like a nice cold Zima on a spring afternoon. Refreshing. Beautiful.

I did not realize the Columbia can give me feels like this. But it does. It surely does.
If you find one, make sure it's gone through. You can get all the awesome stuff and advice from this guy: https://www.columbiatwospeedparts.com/index.cfm

Blake luckily and badassingly used this guys stuff when putting the columbia in his/my 39. It's like the coolest thing ever.

 

That thirty nine is perfect

 

Gorgeous '39!!

 

While I was exchanging emails with Jim Brierley he told me that in his experience the flathead motors like higher rpm’s than most of us think. At least speaking for myself here are my thoughts (1) any hot rod is a sink hole for $$$ so fuel mileage is the least of my worries (2) it is not the motor that dislikes the higher rpm, it’s my ear that can’t stand it. 50 years ago I ran a 57 Chev pu with 411 gears all over the western US at 80 mph (around 4,000 rpm as I recall) and never had a problem. Now it would drive me insane reaching for another gear all the time. Harley owners begged for another gear for 20 years before Harley came out with one and it had nothing to do with better performance it was the “seat of the pants” thing. Same with the Honda Goldwing. We have been spoiled by overdrives that have now been the norm for 30 + years.

 

And for the most part better traveling roads…In 1955-56 the normal highway speed limit was 55 and the rear gear in our family cars was 3.21’s.As more of the interstate system was finished it’s now as high as 75. I have that same mid 50’s car today with the same stock engine and installed a rear end with 2.74’s and couldn’t be happier.

 

Columbia all the way! I had one , stored for thirty years, that I bought from a salvage yard that was closing. But I finally sold it and shipped it to Australia to finance my long tube 65 FE iron exhaust manifolds!
It will give you 4:11 to one and 3:00 to one!




Bones

 

Yup. I don't see the need for overdrive unless you plan on running 80+ for days on end. I'm running 3.78 gears too.

 

Thanks guys!

 

I think you'll find it's over $3,000 now and there is a 6 month+ wait time. Great OD though. I've got one in our 29.

 

Happy new year to all of you,
has someone of you an idea what kind of overdrive this is which l would like to install together with a 39 gearbox in my 29 coupe?

 

Borg-Warner adapted to a torque tube.

 

Find a S-10 4X4 transmission and use this guys kit which retains the closed driveshaft.
Vintage Metalworks

 

There was a guy building those Borg Warner/torque tube thingys back in the 70's & 80's. I forget the name, but he made quite a few. They show up occasionally.

 

I was fortunate to know Dan Kreible, RIP, and had him put together a Columbia for my '32 Roadster. It is absolutely a kick to drive, put in the clutch, hit the rocker switch and listen to the click as it engages the overdrive. Makes me laugh every time because it's so cool. It made my Roadster a freeway flyer and 70 mph is 2,000RPM. 3:78 to 2: 76 it's perfect!!!

 

I have a Mitchell in my '47 and I have a very similar Borg Warner adapted to a torque tube like the one above in my '40. The Mitchell is a little more simple and a lot more fool proof, and also probably a lot stronger, but the Borg Warner is living behind a Caddy motor and has been holding up fine for a few years (stronger than the 3 speed I destroyed with it). If you can find a Borg Warner I would run it again, when you find them they are a third of the price of a new Mitchell.