Anyone know the metallurgy of a 901 stub axle to the transmission

[Chris Pomares]

I've had a pair of stub axles that were made up to attach a mag case 901 transmission (69-71 and 914) to SWB axles on my car for 10 plus years. I'm looking into having these machined as one piece for a second transmission being built. I want to use steel or stainless steel that's as good or better than the original. Anyone know what steel was used?
Does anyone know what these notches are for? Some kind of tool?
Also if these would be of use to others let me know please.

[Chris Pomares]

Anyone have a suggestion of someone I can call?

[gled49]

California Motorsports. When I was there, he was making all kinds of drive flanges.

[xpensivewino]

For what it’s worth my father in law took up knife making and forging. He asked me for some scrap automotive steel from my projects, so I gave him a 901 main shaft I had. He said it was the hardest steel he’d ever seen, and created a balde that could stab through a boat hull !! Lol

[Jon B]

Does anyone know what these notches are for? Some kind of tool?

Chris, the notches indicated the proper alignment of the flanges with the CV joints, which had corresponding marks.
See the last paragraph of the service bulletin below...





Jon B.
Vista, CA

[Chris Pomares]

Thanks Jon!

[Chris Pomares]

8620 cromolly then maybe heat treated.

[Olivier]

Good infos about this steel:

https://www.google.com/url?sa=t&rct=...9Ze4pqEg_fs5XG

It's main advantage is that it can be Carburized. Perfect for gears, where the parts will wear a lot under friction.
Maybe a bit overkill for drive flanges. Indeed the splines will see some kind of funny load cycles, but nothing really comparable to what happens with gears.

There's a "general purpose" high grade steel here in Europe called 35NiCrMo16. Don't know what its AISI equivalent is, but it's supposed to be good for driveshafts... I'd go that way, and I'd discuss the heat treatment with the machine shop you'll use. I'd go for a mild temper/quench
https://www.google.com/url?sa=t&rct=...cZIk8QVZcTK5El

Hardness is great. But toughness (impact strenght) is better in your application, plus, take great care about tolerances and surface finish on and arround the splines (this is where the parts would fail)

Good luck with your project. and let us know what you'll use.

Olivier.

[uai]

42CrMo4 or similar in German it's called Vergütungsstahl
Also possible with a bit of nickel or vanadium
The question is nitriding or case hardening - then 16MnCr5 or similar depending on heat treatment you can choose the material.

[Chris Pomares]

Thanks guys for the input. I'm looking at another option.
I spent an hour or so with my machinist measuring a mag case 914 and LWB 911 stub axle and a SWB stub axle. The only difference in the two as far as inserting it in the diff is the SWB is 34 mm and the LWB is 35 mm. The splines are the same and the seal surface diameter is the same even if the 914 seal surface is longer. I've heard of welding up cranks and cams. Could I do the same here to the SWB stub axle?
The spline end hole will need to be cut a little larger to mimic the end of the LWB piece.
The other option is to sleeve it but the sleeve would only be .5 mm's thick. Heating the sleeve and dry icing the stub axle. I was hoping the splined end was like 31 mm's. Then the area in the red square could have been turned down a bit so the sleeve could have been 1.5 to 2 mm's thick. No luck.
Welding it up seems like the most elegant solution if it's possible. Then heat treating.
Lastly making up another set like the ones I have.