915 Axle Flange Seal Depths?

[David Inc.]

So I noticed a pretty nasty leak coming from my transmission, looking like it was from the axle flange seals.

I'm installing some new seals (and dealing with a stripped CV bolt god damnit mother****er ****ting *****) but after installing the first I think I may have screwed up the depth. I'm not sure, though, because while there's a spec on this it's not clear to me and I see it referenced differently.

This is a picture of the old driver's side seal before removal, with my scribbles on top.

The red lines on the right represent the surfaces from the face of the transmission, down to the first step, and then down along the sealing surface. The blue line represents the depth of the old seal (flush with the stepped surface, installed by an indie shop) and the green line represents the depth of the new seal I put in, about 3-4mm lower*.

The red circle on the left shows the shiny surface on the seal where I bet the flange was rubbing on the seal before, so I guess flush mount is too high, but is 3-4mm too low? I don't think it bottomed out against the differential, and when I put the flange in I could feel it go through the seal, but looking at the flange now I see more shiny metal sealing surface than I'd like. I've seen people talk about how the driver's side is 2-3mm "lower", but "lower" than what? the stepped surface? The top surface?

Am I overthinking this? Is it now a "drive it and see if it leaks", situation?



I don't have near the time I used to have to figure this stuff out, so I look to the brain trust. I'd like to get the car driving again before the end of the driving season.

* Why so low? I whacked it wrong, got it crooked and couldn't pull it back up without damaging it. That's what I get for being in a hurry.

[David Inc.]

I'm going to bump this just one time while I'm waiting on a couple of parts--otherwise it's just "watch to see if it leaks and keep my fingers crossed."

[Otter74]

I need to replace a leaking axle seal on the driver's side and around May, when I bought the seal, I recall finding a post that said there was no real set depth for the seal, and flush or a couple mm down were fine. However, I can't find whatever reference that was because I didn't save a link. I will go with whatever the manual says.

[David Inc.]

Unfortunately the manual says to use Porsche special tool 9***C which is no longer available.

I saw someone else on the forum had made one on a lathe, but that's beyond me.

[David Inc.]

Well now you have me thinking. Checking this thread he shows the dimensions of the tool.

https://forums.pelicanparts.com/porsche-911-technical-forum/387660-915-output-shaft-seal.html

Double-checking the dimensions of the tool and the seal, I can see that the pressing face diameter is 67mm (the seal OD is 68mm), and that face goes 2mm past the stopping face, which is 76mm.

I guess that's the answer, 2mm. Probably, since there are varieties of covers and diffs. I can make a PVC press with a washer to match, I bet.

I have new triple-square CV bolts and Porsche seals on the way to do the other side and replace this one if I've buried it too deep and ruined it.

[Matt Monson]

What that makes a seal to is the axle flange. Load the axle flange in there and make sure that it's adequately overlapping with the step on the end of the flange.

[gled49]

I have a variety of carrier shims that I add to the factory tool to adjust the depth of the seal. Then I test fit the drive flange to check for seal contact and to make sure it doesn’t hit the bell of the flange.

[fanaudical]

Be sure to check the shaft for wear marks / pitting where the seal will ride. You may need to speedy-sleeve that if there is enough pitting to quickly erode the next seal.