915 flanges with 930/turbo spec car. 100 to 108 mm Help!

[Speedster_]

Hi everyone!

I have a problem when building up my car from different year models. I think my rear part suspension is from a turbo specification car from -83 (I think) where the outer flange is 108mm. I also think that I have the correct (nut sure) drive shafts for the car. They measure 108 mm in the joint.

The problem is the 915 gearbox that is from an older car and have 100 mm flanges. How do I solve this in the easiest/smartest (consider cost...)??

Is it possible o find flanges from a spec. car from -83 and change them?
Is it possible to take the CV-joint 100 mm and mount it to the drive shaft or is the drive shaft different in diameter?
Is it possible to machine/weld the 100mm flange into a 108 mm?
Is there any other model that I can get the flanges from and modiy hem?

I really appreciate all the help I can get. I have googled this and read a lot of threads on Pelican but still I’m confused?

Joint 108mm (I think these are the correct one to the car)




Flange at the wheelside (108mm )



Flange at gearbox (100 mm)

[19-911-65]

This post may help out with at least some additional info:

CV and Axle Cross Reference

[Matt Monson]

930 turbo/later 3.2 915 flanges will bolt to your gearbox.

[Speedster_]

Originally Posted by 19-911-65

This post may help out with at least some additional info:

CV and Axle Cross Reference

The axle on my car is 275 mm long and 30mm "Spline OD" but with a 108mm/6 bolt CV so its not in the list. It looks like i have the 69-75 axle lengt and the Turbo CV. Can that be the set-up if the car is sold with turbo-spec (but not a turbo engine)?

[Speedster_]

I will look in to if it's possible to weld an extra 10 ring on the gearbox flanges and drill new holes. Should be a quite easy thing for the right company.

[spuggy]

Originally Posted by Matt Monson

930 turbo/later 3.2 915 flanges will bolt to your gearbox.

Matt, the late factory 108mm flanges are like rocking-horse poop to find used (as they only used them for 6 months before switching to G50, IIRC). And the Albins ones were $400 a pop a few years ago.

But 930 flanges bolt-in to a 915? Never knew that.

[Matt Monson]

They are basically the same flange, the. 3.2 and 930. G50 can also be shortened to work.

[spuggy]

Originally Posted by Speedster_

I will look in to if it's possible to weld an extra 10 ring on the gearbox flanges and drill new holes. Should be a quite easy thing for the right company.

Speedster,

You can also remove the stub axles from the wheels.

Then you could replace them with stub axles with 100mm flanges, and use the stock axles your gearbox wants.

I think I may have a set of 100mm stub axles I have no use for if you want to go this route..

Or replace the gearbox flanges with 108mm ones, and either run:

* axles with 108mm flanges both ends, or
* G50-style axles (incorporate a non-removable stub axle and don't bolt-up on the wheel side).

Probably depends how much power you're making/how hard you put it down which is the best course for you....

[Tom '74 911]

Originally Posted by Matt Monson

They are basically the same flange, the. 3.2 and 930. G50 can also be shortened to work.

I went through this a while ago when I put an early 80's SC 915 gearbox with an OS Giken LSD into my '74 911. The stock '74 915 uses 108mm flanges, but has coarse splined flanges. The OS Giken LSD only accepts the later fine spline flanges.

In the end, I used G50 flanges which had to be machined down slightly to fit as they were too long. Not hard to do and a good end product, but a few extra steps involved and not the most affordable route.

The path of least resistance and likely most affordable way to go is to convert everything to 100mm flanges I think. I chose to stay w/108mm flanges because I have a 3.6L engine in the car. I have no idea if they are actually, in real life, are stronger or not...

Tom

[J0hnny]

Originally Posted by spuggy

Matt, the late factory 108mm flanges are like rocking-horse poop to find used (as they only used them for 6 months before switching to G50, IIRC). And the Albins ones were $400 a pop a few years ago.

But 930 flanges bolt-in to a 915? Never knew that.

I went through this...

Ended up buying a different transaxle with the 108 mm flanges, the late 108 mm fine spline output shafts (flanges) are unobtanium.

I want a spare set, just in case, I'll try to reach Albins and post pricing.

I've seen this topic pop out a few times, it would be interesting to see how many people is in the same situation.

[Speedster_]

Thanks for all the information, I feel lika have some answers but still I don't know which way to go, I hope this won't stall the project.

Here are some pics from todays work.

This is the stub axle from the car, this seems to be same as 930 so then it is difficult (or?) to change the setup to a "100 mm" set-up?



This is the flange from the 915 (100mm) and after your comments it looks like the best solution would be to find G50 flanges and modify them.

[Walt Fricke]

Matt knows this stuff backwards and forwards. And you have advice from guys who have done it. The absolute last choice would be to try to modify through welding and drilling and tapping a steel part for this application (other than just shortening something). You don't have to do that.

I once had adapters made so the 100mm CV flanges would work with a Spicer U joint axle on a 915. The original was for a 901 transmission, where the Spicer was a popular race modification for the Nadella joints. Worked fine. But expensive, and eventually I changed everything over to CVs - much better than U joints for the application.

If I got stumped on this, I'd look into having axles made for me which had the splines on each end for the CVs which would fit what I have. You don't have to have flanges on the axles - the splines can just be longer, and the CVs can float on the splines instead of being clipped fairly tightly into one place on the inner CV. That would take care of different CV thicknesses.

Though there is something to be said about having all the CVs the same - fewer spare parts needed in the trailer.

[KTL]

Originally Posted by spuggy

You can also remove the stub axles from the wheels.

Then you could replace them with stub axles with 100mm flanges, and use the stock axles your gearbox wants.

If he has 930 trailing arms, which use the 930 multi-piece bearings and different length stub axles, then the std. 100mm stub axles won't work.

[Matt Monson]

Originally Posted by Walt Fricke

Matt knows this stuff backwards and forwards. And you have advice from guys who have done it. The absolute last choice would be to try to modify through welding and drilling and tapping a steel part for this application (other than just shortening something). You don't have to do that.

Thanks Walt. I appreciate the vote of confidence. However, my area of expertise goes in-board towards the gearbox. When we get out into the CV realm, I follow these threads because just when I think I have it figured out, I learn something new about axle length or outer flanges.

I agree 100% with the latter part of your comment. Don't start welding up things when stock parts will do the job. These cars are like Legos. You just have to know how to click the blocks together.

That said, I've got a unicorn. He's been in cryo stasis for few years. Kind of sounds like I need to wake him up and get him to start pooping again.

[Walt Fricke]

Matt - you and I are on this same page for sure: "just when I think I have it figured out, I learn something new "

[Speedster_]

Thanks for your input!

I’ll try to understand everything but there is a language barrier when it comes to technical words so I might ask the same question twice

So the last option is to create adapters or modify the flange at the gearbox, what is my option except getting hold and modify a pair of G50 flanges? Or is that my only option in this case since I have the 930 trailing arms with 108mm stub axle?

Remember that this is basically a street car and I would probably never have more than 250 (at least under 300 horse power).

[CBRacerX]

I had this same setup on a race car. 930 trailing arms and axles with a 915. I got the g50 trans side flanges and had them machined down a bit. Done.

[Speedster_]

I had this same setup on a race car. 930 trailing arms and axles with a 915. I got the g50 flanges and had them machined down a bit. Done.

Ok, I'll try to get hold of a pair of G50 flanges!

[Speedster_]

Do I need to change the sealing also to a G50 sealing (if I go for the modefied G50 flanges)? I think i rember reading that somewhere... good to know if a need to order new ones.

[uwanna]

There are two types of fine spline 108mm flanges as shown in this Tech Bulletin. The pre '84 930 version which has a gasket relief and is installed with a gasket. The second type is the '85 1/2-'86 Carrera later and 930 which use a "tin cover/end cap" over the CV joint and use no gasket. On the Carreras, the axle used has no "stub axle" but the outer axle stub/CV is friction welded on. The 930 still uses a bolt on stub axle. It looks like you have an axle for the earlier 930 setup and need the earlier 108mm fine spline flange with gasket relief.
Couple of years ago, when I opted for the larger axles on my 3.6 '80SC transplant,
I searched for fine spline flanges. I first found the earlier gasket style, but found there was no way to make them work with the "tin cover" CVs. Luckily I later found the correct 108mm flanges for my axles. I subsequently sold the older style ones on Ebay, where they were snapped up quickly!
You could probably make the newer style work but I don't know how you would accomplish a non leaking "grease seal".
Don't mean to complicate your dilemma, but you need ALL the info!