Technical The elusive '39 Ford transmission

Let me start out by saying I have searched and researched this site and the internet. I have both the Vern Tardel and Max Navarro books on the subject. But, I still feel there is information out there to be had.
I'm wanting to build a '39 transmission to the strongest it can be built. Oh, I have no grand elusions that a '39 can be built to be bulletproof. I understand there are stronger transmissions but, the '39 is traditional and I happen to have 24 of them. (top shift, side shift, open drive, closed drive, etc.) Yes, I also know there are stronger traditional transmissions but, I want to just focus on the '39 Ford.
In my research, I ran across a book "Hot Rod Handbook" by Griffith Borgeson. On page 72 of this book there is an article called "Racing Conversion for Ford Transmission". In this article they talk about the "tricks" to do to the transmission to improve its strength. I thought as I read this article "this is exactly what I'm looking for". One of the things they talk about is annealing the gears and shafts from 58-62 Rockwell hardness to 35-40, making the gears more able to absorb some shock. I looked into this and found out I need to remove the copper bushings from the second and reverse idler gear before they can be annealed. No problem.......but, nobody makes the bushings to replace them after process. I also talked to a buddy who has experience in rebuilding these transmissions, he said he has his gears shot peened to remove stress but, that doesn't change the hardness.
No, I'm not racing but, my current 8BA Flathead is pretty healthy and the next one may be even more so. I know to set the gears up with little to no clearance. I'm just looking for real world "tricks" or suggestions or direction or something I can apply to rebuilding a couple of these '39's to withstand a little abuse.
Anybody out there have anything to help this learning conversation?

 

I can tell you from experience that tolerances need to be tight. I've also read about guys swapping gears from a late '50's Ford three speed, obviously there is some machine work that needs to be done for that to work.

 

OK, you need to get Mac Van Pelt's transmission book. It is the best one out there. Like Automotive Stud mentioned, tolerance is key. Get things to the lowest side possible. That said, be prepared to install and take apart the transmission a few times in order to get this AND still have it FEEL good while turning things by hand.

I would also suggest using only NOS or good used Ford main and reverse shafts. These are hardened where new replacements are not. I would also try to source the best front and rear bearing you can. USA-made being preferred, but good foreign made like SKF's are OK too.

Lastly, use the best case you can find. One with no ridges in front or rear thrust surfaces.

I have also heard others using the later diamond-tooth gear sets, but I don't know what's involved in transplanting them into a '39 case.

 

my buddy works at a place where they have punch presses and he told me they sent out the punches to get cryogenically treated. he said it was very significant difference in how long they lasted. something to look into

 

I can't add much as for tricks. I'm sure you know to pitch the cages on the Shaft bearings so you can add more rollers and on installing the front bearing retainer to add appropriate shim that you'll have to hand make to fully clamp the bearing snap ring in place, so the input shaft doesn't shift fore and aft. As for the copper bushings from the second and reverse idler gear I would think that's just starting with proper Bar material and making new ones as needed. I don't have one in front of me and if I remember right, they have light perforation to carry lube to the shaft. That can be overcome by cutting spiral groves in the inner surface going both directions or using oiltight bronze material.

 

WOW!

 

As far as bearings go, I'm sure most of us are old enough to remember when "Made in Japan" meant junk. Japanese and German bearings are some of the best made today, most definitely better than Chinese or Mexican for the most part. Sadly "Made in USA" doesnt mean what it used to. Thank the bean counters for that. Good Luck.

 

Good point. By US made, I'm talking new old stock from the good old days. Since these bearings are open, there is no grease to go bad inside.

 

There are a few things to note - as I'm very experienced with these transmissions:
1) You need to start with as good of a main-shaft as possible. There can be no wear on the front bearing "snout".

a) Source your gear-set first (hopefully 25T Zephyr - see below)
b) Put the front input-shaft in a lathe, put the caged roller bearing in the middle and install the main shaft (hanging out in space). Take a dial-indicator and see how much side-to-side play you have in the end of the main shaft (pushing it back n' forth by hand).
c) Select the combination with the LEAST amount of side-to-side movement.​

2) Have 2nd gear re-bushed with a tight clearance to your specific main shaft - it should "drag" just a bit when you turn it by hand. This is a custom process - you may want to have 'Charlie Schwendler' re-bush the 2nd for you (he has done about a 1/2 dozen for me). He will need the specific main-shaft and 2nd gear combination you selected up above. eMail: cas5845@yahoo.com
3) Set the stack-up clearance for the gears and synchro hub on the main shaft to have only about .002 end play. You can achieve this with various thrust washers and may have to use a surface grinder on the back of the 2nd gear to get everything just right. There are different thicknesses of thrust washers . . . seems they are never quite right, so I tend to tune things with a surface grinder.
4) The strongest gear set you can use is a 25T original Zephyr setup. They are hard to find and make sure you have a complete set (cluster, main shaft and 2nd). The gear that is easiest to break is first . . . ask me how I know this! The problem is when you break first gear, you ruin the cluster . . . . there goes a $1200 gearset.
5) Install a hard-stop in the shift tower for 2nd gear actuation . . . such that you don't overextend the slider when you push into 2nd.
6) Do not use the repop main cluster shafts - they are .001 undersize and not correctly hardened. Since you have a bunch of transmissions, find the best shaft you can - if worn a bit on one side, flip it over.
7) You can stop the leaking issues by putting o-ring grooves in the main and reverse shafts as well as sealing the rear shaft pin (shorten it and plug the ends).
8) Have the case baked and shot peened - the cleaner the better.
9) As others mentioned - you're usually FAR better off with original Ford bearings (especially the caged rollers) than any repop stuff.
10). Talk to Mac VanPelt about parts - he's a solid dude and will help you as best as possible.

 

Bored & stroked, Et al, I talked to my machinist about the undersized cluster shaft, he suggested using an original shaft and having it hard chromed and ground. Thoughts? In addition, I had a conversation with a gentleman that drag raced flatheads back in the day. He said one of the things that he did to enhance the longevity of the trans was to copper plate the gears to tighten up the clearances. Has anyone done this lately?
Tom

 

Bored&Stroked do you have any insight to an old wife's tail I have heard on more than one occasion that removing every other pointed Sincro tooth will help hard street shifts engage?

 

Man, I haven't had anything plated that recently, but I'd assume copper & chrome plating those parts would add an addition $750-$1,000 to the rebuild.

At that point, I'd ask myself is it worth it?

I built my latest trans being crazy about clearances. I'm not easy on it, but it continues to work flawlessly. I think it helps that I run bias plies and the tires spins rather than grip.

That said, we need to remember these boxes were used behind OHV and baby Hemi dragsters back in the 50's/60's and survived race day.

 

RE: That said, we need to remember these boxes were used behind OHV and baby Hemi dragsters back in the 50's/60's and survived race day.

That is true, but I also wonder how many started out in 1st gear? I bet many of them started in 2nd? My issues have always been with 1st gear and the cluster.

 

I've never really had synchro issues, more along the line of basic strength issues . . . especially between 1st and the cluster gear.

 

I've read guys taking 1st gear out all together for weight and, to your point, starting in second. I've often wondered how that worked. Do you put in a "plug" to take up the space? Don't want to derail the thread...

 

No, you just don't put the 1st gear slider on the main shaft . . . nothing to it.

 

Ah. That makes a lot more sense. LOL!

 

In the 70's a lot of serious drag racers did remove every other tooth in the 4spds for a better shift [every other tooth on the gears and every other tooth on the sliders to depth of engagement], some [most] even left out the brass syncro rings, thus crash box and always had to shift quick or double clutch like a Model A when shifting slow... In my case with a Ford Top Loader 4spd with full tooth count and stock syncro rings I could shift at 7000 rpm with right foot left to the floor and tap the clutch. Only missed second gear once; my fault. If you do remove teeth you will gain some back lash which maybe noticeable. Overall I don't think It would hurt.

 

""That said, we need to remember these boxes were used behind OHV and baby Hemi dragsters back in the 50's/60's and survived race day""

And the yards were full of them

 

You might look into www.negearpolishing.com or similar process. I had a 9" gear set [nascar] and they looked like they were chrome plated.

 

An old time early Ford tranny guy built several with Thunderbird gears, fully synchronized. As far as I know only one is still unused and the guy who has it wants a $1000, so there it sets.

 

There was a write up in Ford Barn [I think] telling how to use 50's gears in the early trans, maybe even OD too..

 

True, but by that time other manual transmissions were options too. Must be a reason a lot of them stuck with it. Banjo rears as well.

 

Great info, thanks guys, I have a couple to build & a 50's box to pull apart too

 

This is all very good information.
Automotive Stud - I didn't know about using later '50's gears but, why? Did the material or Rockwell hardness change?
Tetanus - I had lightly checked into cryogenic treatment but, didn't think it was the way to go.
Pist-N-Broke - I did not know about removing the gages from the needle bearings. Curious how well that works. I have a lathe and mill and had entertained making my own bushings but, seemed like a lot of extra time for something that should be available.
Bored&Stroked - All very good information! What makes the Zephyr gears better?
hotcoupe - The article I referenced talked about copper coating the gears to even out the heat treating process and I realized this would tighten tolerance but, I was concerned that copper was too soft and would wear and/or flake off.
seb fontana - I did not think of micro polishing.....interesting idea. I'll look on the Ford Barn about the '50's gears in the '39 case.
Since this is a street car, I'll keep all of the teeth on the gears and sychros. I'm just trying to build a stronger street transmission not an all out race tranny. And, yes, the first gear/cluster are the biggest concern for me. I sheared 9 teeth off of the cluster gear after already feeling a "click" in first gear. (Chipped tooth)
Again, really good information. Lets keep this conversation going.

 

I can’t help, but just a question.
Do you have 24 ‘39 transmissions, or 24 transmissions total?

 

I'll take a stab at this. The 50's trans gears are known as "diamond toothed" gears. Supposedly, they mesh a little better/tighter and have different ratios, some say a little better ratios, than early Ford. The reason why LZ's are a tad stronger has to do with the somewhat reduction in force that is created by the gear ratios. Make no mistake about it, LZ's are not that strong and will go south of the case under a heavy throttled side step of the clutch

 

BanjoRear has it right on the Zephyrs. The torque is not as heavily modified with the 25T cluster gears versus 28 or 29 tooth cluster gears. And as he noted, they're not bullet-proof by any means - I have two "stripped" cluster gears in my shop as paper weights! The bad part is these gear sets are very expensive (if you can even find a 25T set) - so ruining a set of them is a costly adventure.

 

Not that it helps anyone,, just blowing my horn:
In '72 I was handed a set of gears and told to grind off each other tooth.
At the start, the first 3 teeth were works of beauty. After that 'just get r done'

 

Hahahahaha