930 (108mm) output flange identification, Two pair with different seal landing dimens

[pcar916]

Anybody familiar with the two 108mm flanges in the pic below?

Both (on the right) are 108mm course-spline flanges. But as the pic below shows, the center flange has the same dimensions as the 914 flange (left) on all turned surfaces.

The 108 flange on the right is the same dimensions (on turned surfaces) as the 100mm SC flanges I use with 944 cv's on my 914.

I can just barely make out what I think may be the part number on the rightmost flange.

915.332.209/01 but this may be incorrect. It's not distinct.

Anyone run into both at some point? My guess is that the flange on the right is from the SC era and the center one is an earlier turbo, but I'm basing that on the SC dimension match, not from actual fact.

Ideas?

[KTL]

Paul Guard (Geary) was kind enough to share this document. Hopefully it helps you narrow down where your stub axles originated


Coarse or fine spline lsd





So what that image tells you is that all 930 stub axles & diffs are fine spline, because the doc says '75-'88 930 are all fine spline.

The only coarse spline 915 diffs were pre-1978

[pcar916]

Thanks Kevin. I actually got that graphic as well with my GT LSD that fits in both of my 914 and mag-case 915's. So I can use either of the course flanges in either box if I thought the 3.6L engine put out enough torque to justify the extra weight.

But Porsche may have used the longer (middle) 108 flange in another application (i.e. a 906 or something) that I'm just not familiar with. Maybe it's an aftermarket thing. Somebody out here surely knows!

That center flange is ~1/4 in longer than the rightmost one and it's all in the seal boss.

[Matt Monson]

Those longer flanges are worth money. This should explain why...
Limited Slip Differential

Regards,

Matt

[pcar916]

Eureka and thanks Matt! Now I know what they are and have to see what they're worth just because well, I want to know. But I may use them instead.

I don't have a ZF unit... but I did recently trade a crankshaft for a fine-splined Quaife diff to use in my '84 915. Do you know enough about the Quaife that I have to use the 61mm flanges with it, or can I use the open diff flanges? I'll query Quaife if that's not on the tip of your tongue.


OT: I'll PM you separately on another topic about breakaway torque. You told me on the phone last month about the specs to measure on my GT clutches, plates, and belleville washers since I was in there anyway with a broken pinion gear.

I took the diff apart, inspected it and put it back into the transaxle with a new R&P. All GT parts were within the tolerances you specified and disassembly/assembly was as you described.

It's back in the car, working perfectly again and thanks for that too.

Shiny side up!
Ron, Little Rock, AR

[Matt Monson]

I've never known any aftermarket diff. manufacturer to build their product to LSD flange spec. They are all built to the more common open diff flange spec on the models where there is a difference.

As for value? To someone with a real 914-6 with LSD or a '69-73 911S or E with factory M220 option that they are trying to put back together and make correct? About $1000 for the pair of flanges.

Drop me a line when you get a chance. I'm glad that your inspect and reseal went well and you're back at it with the LSD in the car and the ring and pinion repaired.

Regards,

Matt

[Jon B]

Originally Posted by pcar916

But Porsche may have used the longer (middle) 108 flange in another application (i.e. a 906 or something) that I'm just not familiar with. Maybe it's an aftermarket thing. Somebody out here surely knows!

All Porsche sports/racing cars in those days, from 904 through 936, ran diff flanges for Nadella or U-joint couplings, not CV joints...