1939 Trans Rebuild - Shafted Again! (with a twist)
 

A Little Trans History . . .

Okay, so the old and tired 39 box in my 32 Cabriolet finally died (sychros are gone) - can't complain, it lasted a year with a very stout engine against it and I wasn't nice to it either. Hey, built it when I was 15 (40 years ago) - drag raced the Antique Nats with it 3 times . . . it paid its dues and I just threw it in the Cab anyway. Time to build a transmission again - should be fun.

So - now I'm building a 'new' 39 Trans - with a NOS set of 25 tooth Zephyr gears and bunch of new parts from Mac VanPelt (his stuff is nice), some custom 2nd gear work from Charlie Schwendler (special bushing fitment), etc.. The best stuff I can find . . . but I'm not happy about the two shafts - they suck! The original mainshaft has .002 wear on it, the best one that Mac could find has .002 wear on it and the repop shafts are pieces of crap (don't buy them!) -- the materials are soft and they are .002 too small right out of the box (the whole shaft length).

Here is the Problem I Wanted to Solve

Take a look at the mic readings for the old and worn shaft - in the worn area - notice it is .747 diameter (.002 under):

Attachment 290443

In then measured the non-worn area in the middle - notice the .749 diameter (is what it should be):

Attachment 290444

So I ordered a nice new replacement shaft (thought I was ordering the right stuff) - nope, you can cut it with a file and it is .002 under to start with (.747). Not only will it add slop to the cluster, it will leak oil all over the place. And to think - folks sell this crap (didn't get it from Mac)!

Attachment 290451

Well - time to get shafted my friends

I have some high quality shaft material, hardened to C60 and micro-polished to a mirror. First I used a carbide milling bit to cut the surface, then drilled the necessary 1/4" hole (carbide drill). Then I cut the shafts to length with a cut-off saw and then turned the ends in the lathe.

Attachment 290439
Attachment 290452
Attachment 290440

The diameter of my new shafts - exactly .749 - what they should be.

Attachment 290458

A New Way to Stop the Leaks . . .

I've seen all the methods that folks use to "stop the shafts from leaking". The typical method is to clean the heck out of the case (front and rear) and dab a bunch of silicone sealer on the ends of the shafts and the cross-link piece that holds them in - see below. This works fine - but I don't like it:

Attachment 290446

I'm just not going to bank on that working for long. Hopefully I'm building a transmission that will stand the test of time and be around long after I'm gone . . . so why not come up with a new (and hopefully better) way - well here goes:

I tapped the ends of the shafts with a 10/32 thread and made a set of three end-caps out of aluminum to place over the ends - they have a recessed area on the back sides. I'll put some gasket sealer inside of them before I put them on and also use a bit of locktite to secure the bolts. This should stop all potential leaks from the two main shafts (but not the lock-in shaft that holds them).

Attachment 290441

Attachment 290442

Attachment 290448

Attachment 290445

Attachment 290447

Okay, so what about that little lock-pin/shaft that holds them in? It will leak oil as well - so I decided to tap the ends in the case. I'll cut the little shaft down a bit and then use these allen head screws (with sealer) to seal them up.

Attachment 290449

So - there yah go . . . two new correctly hardened shafts (with good shafting steel), that are of the correct diameter . . . with a innovative way to seal them from leaking.

Guess we'll find out how all this stuff works . . . time to complete the rest of the tranny!

B&S
Vintage Horsepower

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Nice fix!
So did you make a bunch of extra shafts while you had it set up? (Hint hint):)

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Man, you've put some really slick thinking into those, not to mention actually making it happen. Your write-up and camera work are spot-on, too.......first class all the way around! DD

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Dale,
I'll bet Mac Van Pelt will soon carry these in his catalog.......it is a slam dunk.
I think if Mac specified .749/.7495 most of the leak situation would go away.
As we spoke a little while back what is being sold is pre ground Thompson
3/4" round stock. Easily machined with plain old high speed cutting tools.....not
right !
Charlie ny

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

I have gotten the reproduction shafts with a groove at the end for an O-ring, The shafts are hard and proper size, the o-ring works well, there is still a very small amount of seepage, most likely from the retaining pin.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Dale:

Awesome. Thanks for sharing. Love it!

Tim

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Terry,
Who was the vendor ?
Charlie

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

I know Hot Rod John sold shafts like that.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Yes its what I found the shafts that I got last time came from Joblot [I can say that now] barely made spec. I did let them know at the time. James agreed.
We really need the right shafts , would certainly help the leaky problem.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

I'd be interested in anybody who has high quality shafts, made with the right materials, the right hardness and the right size. Anybody know of a source?

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

One thing I found in my cases was the hole in the case was worn oversize.
I bushed my cases.
Lawrie

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Are you talking about C 60 Rockwell Hardness? Unless this is NOT hardened through I want to know how to drill and tap 10/32?

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

John,
Appears to be case hardened. Even 1020 carburized hardened and ground
will work just fine, a proper case goes .06. If I still had access to a centerless grinder
I'd be poppin' these babies out and they'd be 1020 steel carb'd, hdnd and grnd.
Charlie ny

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

That is some SERIOUSLY nice work! Love the small screws you added to the lock-pin bore. That ought to keep things nice and dry. When I rebuilt my car's trans we used hardened drill rod to make a new main shaft. So far it's worked flawlessly.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

I have some NOS shafts in the Ford boxes if anyone needs them to verify hardness and or dimensions. I'd be willing to loan out. Just PM if interested.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

It is definitely not hardened through - or I'd have broke off the first tap and called it a day! LOL

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Does anyone know the quality of the o-ringed shafts sold by Hot Rod John, the E-Z Steer guy in Ohio? I've read some not-so-good things about him. If the shafts are good quality it is a reasonable way to stop the seeps.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

I was thinking too about drill/tap the shaft ends, but knew I would break drill/tap, so thanks to the guys here, I found a post that suggested grinding 1/8 of the end of the shaft and fitting a 3/4 welsh (freeze) plug .

I ground the ends of the pin holes flat and put some booker bar (all thread) bolted thru with some gasket /washers and sealer.

Running synthetic oil and zero drips so far.

http://i86.photobucket.com/albums/k1...psgdagvk4s.jpg

http://i86.photobucket.com/albums/k1...psdfirkylj.jpg

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Thank you all for posting your methods and suggestions. You can't argue with success. I'm putting a transmission together now and struggling with sealing these shafts. Before tearing this transmission down I had a drip pan under the transmission to catch the oil from the countershaft. I want to eliminate that, just have to decide the method.

Re: 1939 Trans Rebuild - Shafted Again! (with a twist)
 

Nice work - that was the other method that I was thinking about - seems you've done it and it is working - thanks for sharing it!