Technical Early ford trans damage

There are a lot of threads on here warning how risky it is to put an early Ford trans behind later ohv engines. I am curious if those of you who have broken them could shed light on what the usual failure mode is if there is one. Some threads say the cases crack, some say gears strip, etc. Where do they typically crack? Do most failures happen on hard shifts or just acceleration? Are certain individual gears more vulnerable than others 1st vs 2nd? Are closer IE 16 vs 14 or 15 tooth boxes stronger? @Mac VP has seemed to say that the late 51-52 gear set profiles are marginally stronger. Is this a factor of profile or the loose needle cluster bearing design? Some guys say watching end play is key to case life. Do you just stick to the close end of the ford specs? Also it seems like from looking at part numbers that the 51-52 input/main shaft combo might let you run gear sets from the 49-54 passenger car trans?

I have all 3 books guys usually reference; VanPelts, Tardels, and Navarros. Just looking for more insights/experiences/experiments guys have tried. Pics of carnage encouraged. Lol

 

Most of them break because they get over shifted ( I do not know if that is the correct term). They have no shift stops, the shift lever gets shoved past where it needs to be to engage the next available gear.

Another thing that breaks them is the fact that they are a non syncro transmission on a synchromesh world. You have to know how to drive one a certain amount of finesse is required.

Next you have to remember that for a '39 Ford ( a popular transmission) even with a wheezer motor you are throwing 200 ponies ( and the torque that goes with that) at a transmission that was designed for 85 ponies 100 HP max.

I have seen more bent shift forks than anything else after that stripped gears ( because you are driving a none syncro tranny in a synchromesh world) If it actually busts the case it is going to be either in the belly ( where the metal is thinnest) or near a bearing when the main shaft is trying to climb out.

Lots of them got used behind early valve in head motors for lots of years. You just have to remember that one that are not a race transmission so speed shifting is out of the question, two they are fine for just driving around (see one) and three if it is already worn out ( which it probably is) you are going to break it especially if you do not observe one and two.

I could go on but you catch my drift right?

 

if you are going overhead, why not use a newer tranny too? IMHO the reason to use the ford is when you are all ford flathead from front to back. so, the original question i cant answer. i have not broken one, but plan to use many more before i am toes up. mildly hopped up flatheads and some sensable driving they work just fine. one of my older friends likes to tell how he blew out the bottom of the case, cluster gear and all, out of a 34 back in the 50's. had to drive home in high gear. i said, had you been beating it all night? he said of course, thats what we did!

 

Most of my failures were broken teeth on the input shaft and cluster gear. I have very carefully rebuilt transmissions with all new internals, then driven very carefully (because I didnt want to break anything) and still had broken teeth so I wont use any flathead transmission against an OHV

 

Thanks guys. That is good info! I drove an early Saab 900 turbo for a few years which requires similar technique if you don't want to have a "cornsheller" experience. I got pretty decent at double clutching and feeling the gears engage even though it was a modern synchro trans. Main reason is I need to stay torque tube since in my early 50s special the drivetrain is above the floor and in between the seats. I may convert a packard to close drive when I find one. I have a closed drive R-11 overdrive housing off a Rambler that I think I could put on an overdrive 3 spd Packard. Then I could make a plate like Transmission Specialists used to sell to put the 39 lid on the Packard box.

 

I don't remember exactly what broke because it was along time ago, 50 years, but I believe it was the cluster gears. I had a 36 Coupe with a stock 348. Ido remember it didn't take much to break it.

 

I grew up with these old Ford transmissions, and other equally non syncro trannys. So for me it is just driving. Vern is older than I am so I am pretty sure that driving one is no problem for him either. yes there are better transmissions, but if you want to use one for whatever reason you just have to remember that it is not a Muncie Rock Crusher and drive it accordingly. The books are written for people that grew up with cars that were designed to be idiot proof. Well that and the Authors are more refined than they were 50 years ago. LOL

Of course my advice may not be appropriate for the average guy. You have to remember that in a world of world class double down 5.6.7 speed whatchamacallits I am putting a Saginaw 3 speed behind the 400+ ponies that push my little car around. Hell I am even going to run the 40 Ford rear until it explodes.

 

If you could find a brand new off the shelf '39 floor shift box and install it behind say a 312 Y-block you could start an adventure in death spiral. The first speed shift would do bad things to the shift forks and synchros. Next will come missing teeth on the cluster gear and input shaft followed by case cracks and oil leaks at the rear part of the case.
If you want a nostalgia look then go with a T5 and bend the old shifter to the shape you want then weld it to the T5 shifter and cover with a nice boot. You will be dollars ahead and a happy camper.

 

I'm fully aware that newer transmissions would be a better choice and if I were building a car from scratch it would get one. On this car though I'm sticking with the original build from 1954 (303 in front of the 39 ford/banjo rear later changed by original owner to '56 324) and am willing to deal with the limitations that imposes. My intent with this post was just to explore what tends to fail on the early 3 spds.

These pictures might help understand why I think having a modern trans would kinda ruin the car.
https://www.jalopyjournal.com/forum/threads/1950s-tube-frame-sports-car.993579/

 

Wow!
The topshift Ford 3 speed is legendary. It's part of the combo. Not only with flatheads but with a host of other engines as well.
It may have always been the weak link but still it does not change the fact that it is indeed oozing with hot rod history.
I love mine. Right now it's the only thing on my F1 I truly love.
It's leaky.
It does not like to coast in second....it absolutely refuses to do so at high speed.
Only I can drive it well....because I know how.
It likes a firm confident hand.
Too hard....trying to force it, She'll balk....
Limp wristed wimpy sissie shifts.....She'll really raise hell!
She likes firm confidence. Do that and she shifts like a 5 speed.
Winding out second is a true joy of mine.
They are not a really good transmission. Mine's only wore out one flathead and 2 302s.

How many transmissions have a Rock and Roll hit?
The Duals knew how to drive one..note no power shifts.

 

Any transmission can go out in a spectacular show gears, grease and fragments. While I was in my dads barn working on one of my projects a neighbor in a 67 F100 was driving by and his 3.03 went capluey with a spectacular display of noise gears and oil...
He was just cruising in high.
The 3.03 has a reputation as one of the toughest ever so....when it's time it's time.

 

My first 'up close and personal' hot rod experience was a ride given to me by an older cousin in a early Olds powered channeled A coupe with a early Ford box. After getting safely away from his parents house he demonstrated just how quick it was, unfortunately his attempt at speed-shifting from 1st to 2nd sent the shift lever and other misc parts exiting up through the top insert, other parts onto the street.... Looking back, it's a miracle that neither of us got hurt. We did get in trouble however when after walking back to their house, we both had 90W on our 'Sunday' clothes...

 

In high school my 50 ford pickup stripped the front gear on the counter shaft twice. It could not have been my driving

 

Okay, no clutch dumping or speed shifting. Sounds reasonable for trying to keep one alive. But what about RPM?

Let's say you have an early Ford box behind a flathead and it hardly ever gets past the 4000 RPM point. Then a freshened up 283 gets dropped between the rails. Now you can twist the new engine out to 5000 RPM's easily. With everything else being equal what will the transmission think about being spun that much faster?
-Dave

 

They tend to prematurely wear out when you put to much power to them.

 

I found broken teeth on 1st slider and cluster gear was common.

 

My little 283 would shell the main drive gear ( input shat ) and the cluster where they engaged. Too much torque taking off. The other gears shelled from shifting adventures. Later Bill

 

They were marginal when new,now they are 80 years old and wore out. My “hot” flatheads used to tear up 2nd gear and cluster gear regularly. Back in the 70’s,bought an adapter from Offenhauser 5272a to put a Chevy 4 spd behind the strong flatheads and many power shifts later—-NO MORE PROBLEMS! Simply put—- if you want to run hard and fast—— leave the early Ford trans and banjo rear end to the restorers or to the 50’s wannabes. NUF SED! This 70 yr old man runs 80 mph in the 1/8 with my Henry 32 cabriolet and it damn sure ain’t no 39 Ford 3 spd trans.

 

I had a nice, tight 39 box in a marina-blue 40 tudor....had a stock 85 HP flatmotor in it. Laying rubber in 1st gear [15 minutes after I bought the car] to impress my girlfriend, I stripped the teeth off the main drive and cluster gear...limped it home in 3rd gear. Last time I ever ran a pre 49 ford trans. I had just as bad of luck with shubox transmissions. And axle shafts.
I always update my old fords with later drivetrain parts now.

 

These transmissions have thier limitations.
If you must drive like dumbass with no respect to your equipment, this type of transmission is not for you.
I don't know what would be.

 

I've got nearly 100,000 miles on my stock 3-on-the-tree behind a mild 283. If you are sorta careful, no burn-outs, no speed shifts, a well put together stock trans might work for you. I really like it. I've broken a cluster gear, and a 1st/reverse idler gear, and replaced syncros a time or two, but overall, it's worth it for me. I have way more tapered axle issues (stock rear end, too) than transmission problems. It's all part of the fun!

 

I made a pretty good side job living in high school in the early '60's, rebuilding old Ford transmissions. I've seen some hang in there forever like fatkoop has stated and seen some scattered so bad that nothing was salvageable. They have failed on stock flatheads and every other engine of the day. After doing so much work on them, I think I found out the REAL reason for failure without reason. Ford made the gears out of a secret combination of wood putty pressure fused with grinding dust to give it that "metal" look. If you have one, treat it with respect and maybe it will respect you. I had a '39 box behind a virtually stock 302 in a '27 roadster. We went Muroc and they re positioned us to south base. They asked us if we would all do a parade lap of the course about mid morning. Off I went and left the line easy as I accelerated, we went through powder and before i got to lift off the throttle we were back on firm lakebed. The engine revved slightly in the powder and as soon as we hit hard lakebed the tires bit and BANG, I snapped a tooth off the cluster! It would have been much more honorable if I had been ripping and tearing across the lakebed like a madman, but no, taking my time leaving the line along with 50 or so other cars.

 

Thanks guys! It sounds like broken gears are way more common than cracking cases. Any thoughts on whether the input tooth count makes them more or less likely to break? Is a 16 tooth more or less likely to tear itself up than a 14 or 15 tooth? Also, how thick of oil are you guys running?

 

Side shift trans behind a 283 with no problems until my dumbass bump started it one day. Broke a tooth off 1st. Mac VP built me a new one, still in a crate waiting to go in.....

 

Here is an interesting article from 1963 I thought might be good to share.

 

That's an interesting article. What is the publication?

To address your question, I have a '39 trans behind a 303 that was build back in '58 or so. When I had it apart to clean it up I noticed the case had been split at the front and repaired. It has been parked for the last 52 years and I recently got it running. I will be babying it for sure!

 

@Bruce Lancaster turned me on to it. He referenced it in another thread so I asked him what it was in. He was kind enough to let me know.

 

My experience with these trannies goes back to 1956, when I blew my first one! But hardly the last...
1.) 1946 Ford Tudor, reversed '48 Merc wheels with 6" Olds rims, 8.20 X 15s. Laid some rubber, and 'Bang!' First gear...I hoped it didn't take the cluster, just the slider...???? Bah! Took 'em both out, but I had gears...
2.) My '32 five window...highboy, complete build. 304" flattie, tranny was a '40 Ford p/u, tight.
Second gear, 'Bang!' Input shaft, cluster. Next one was second gear again, opened the case and cluster dropped out with the bottom of the case. Four more, iirc.
3. I hate to go on...'46 Coupe, 331" Reath Chrysler Hemi, Hansen 6-71. '39 box... LOL
I NEVER blew that one...Nailed it (smoothly) in second, up to 5,5 RPM...scared myself...LOL
Really expected some 'trauma'. But it held 'til the car was stripped in my OWN garage while I was in L.A., never caught the slime. (took my tools, welder, torches, all of it)
There were a couple more, (my '36 Five window, and the roadster...a few more!)
I have one I'm doing now for my tub (flattie) I never learn...

 

Good subject that I have been mulling over also, 48 Ford with a 400 sbc in front of the original 3 speed and banjo rear, its been a (always working on the other cars) and (never enough money to do them all) 10 year project.
Going to insure it and start daily driving it this spring, but I have phase II parts ready just in case.
Picked up a early 1970 Chevy truck the Bell housing, flywheel, clutch,pressure plate + three speed trans also a 56 Chevy rear end for when doomsday comes. Hoping to keep it 3 on the tree with the Chevy trans.

Going to drive it like porknbeaner says and maybe it will stay together. Only using center carb.

 

If the transmission is fully in gear before releasing the clutch,the 39 tranny will hold a lot of hp.its sloppy shifting that breaks them.the skinny rear tires will break loose and realease the energy.i ran a built nailhead back in the day.never had a tranny
Go.

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