question about 915 flange sizes

[notch11]

hello, tried to search this out no luck.

i'm building a vw with porsche runing gear and I have a 915 trans (not sure what year) it has the 110mm 4bolt style flanges.
for trailing arms I have alu. 944 turbo (1986). vw vanagon axles are the correct length but they run 100mm joints(fits the 951 arm perfect.

I guess my real question would be is there such things as 100mm 915 flanges?? if so can they be swapped out with my 4 bolt ones?
I know there is a guy that sells custom flanges. but they are like 400 bucks and it seems that there has got to be a cheaper option.....but maybe not
sorry for the long post but I know if anyone knows you guys would.
thanks ,

[mmasse]

I am not expert at all but I will try to help. I am sure others will chime in.

From what I know the flanges on your tranny should be from the early 915 pre '73, which used 108 CV joints.

You should exchange your flanges for the post 74, which are 100mm. If I am correct there are 6x8mm bolts. The only thing you have to check are the spindles on your flanges, since there are two types of flanges: course and fine. Check with one of the Porsche dismantler guys. I know flanges are expensive but I think $400 is TOO much.

Hope this helps

[notch11]

so it sounds like i need 100mm flanges with the correct splines....with out the # off my trans can anyone tell me if my splines are fine or corse? I could get the # off it tonight....just at work right now.

[Eagledriver]

I'm not an expert but I think the early four bolts were course splined. My 72 is this way. I think but am less sure that the 6 bolt smaller flanges on the SC were fine splines. You could solve the problem by getting a differential and flanges together. Should be relatively inexpensive from a place like Partsheaven.

Actually I think I might have what you need at home. I'll check tomorrow.

-Andy

[mmasse]

Originally posted by notch11
so it sounds like i need 100mm flanges with the correct splines....with out the # off my trans can anyone tell me if my splines are fine or course? I could get the # off it tonight....just at work right now.

Post a pic and we will tell you

[notch11]

alright here we go pics

left is 944t stub rt. is 915 flange

and the pics came out pretty good on the part #'s

[mmasse]

looks course spline to me!!!

[notch11]

So I guess I'll look for a later fine spline diff. what year should i look for? or could I just buy a quiafe for a later 911 and source the flanges from the junkyard?

[notch11]

according to quiafe 78-86 is the fine spline 915 with 43teeth
and 72-77 is corse 18teeth. so any experts out there know for sure if you can swap early and late diffs?? I guess i'll also try another search there are tons of 915 threads on here.
thanks for your replys,

[group911@aol.co]

Seems like they made a coarse spline 100mm flange. I'll look at the ones I have and see.

[notch11]

that would be sweet. let me know what you find

[group911@aol.co]

Here they are. Measure 4" or 100mm

[notch11]

can it really be that easy? those flanges are a thing of beauty

[Grady Clay]

Ok,

Your image seems to show a stub axle that uses a 108? mm CV
joint but the six bolts seem to be M8. Is that the case? Measure
the ID inside the raised lip on the stub axle.

If the bolt circle of your CV joints is the same as your 915 flange,
you might be able to install inserts (casesavers?) in the 915
flange to accept M8 threads.



If your CV joint is 6-bolt 100 mm then it seems like the only issue
is to find the correct 100 mm transmission axle flange
with “course” 18 splines. The critical questions are: Does your
CV joints use six M8 bolts? Is the CV joint outside diameter 100 mm?

If so, you want a flange with a 923 part number. That would
have originated with the ’76 912E but also used on ’77-’83
911s. It cannot be from a 930 or M491.

I think (but may be wrong) that the change from 18 splines to
43 splines happened with the ’83 model 911.


Here are three:



On the left are 108 mm, on the right 100 mm. The 43 spline are
at top, 18 spline at bottom. Of course the one you need? would
be lower right. The one you have is lower left (108 mm CV, four
M10 bolts and two 10 mm roll pins – the flange measures 109.5
mm OD).

It may be a 951 part is most suitable. I’ll try and find out tomorrow.


Best,
Grady

[notch11]

ya the lower left one is the one on my trans
I'm using 100mm 6 bolt cv's and I wanted to have 100mm inner and outer so they match and run all 4 same cv's

[notch11]

went looking for the positive feedback thread to say some kind words about group911 but i'm at work so i'll post here.... smooth transaction with group911 would buy from again.

[group911@aol.co]

Thanks! Let me konw if you have any problems with them.
Bob

[mmasse]

Bob,

I have a '73 tranny which uses the same flanges as notch11's (course splines), and I need to replace them with flanges for a Carrera CV joint (108mm flange with 6x 10mm bolts).

Do you have any of those?.

[group911@aol.co]

Mario, e-mail me at group911@aol.com and we'll try to figure it out.
Thanks