Input shaft seal Problem with 915 Mag case

[Jim Richards]

More on this...

Here's why the input shaft leaks around the seal (observe were it's been wearing against the seal).



And it's interesting that the local p-car specialist drilled a weep hole in my guide tube. It's an 11/64" hole, which seems kind of large to me. Note that they didn't use a "dam seal." But I will!



Also, kudos to Pelican marcesq for showing me how to rip apart a 915.

[Randy W]

Make sure the shaft is true before doing anything else - if the seal is installed correctly, a slightly bent or worn shaft is the most common cause of frequent recurrent weepage on a 915 built before trans #733 7375 (3/73).

[Jim Richards]

Thanks for the advice Randy. I'll have to figure out how to check the shaft for trueness or have it checked.

BTW, I hit a snag yesterday as marcesq and I were trying to replace the main shaft seal. The seals (one for spare!) I ordered from the local Porsche dealer and from Pelican were the wrong ones. Unfortunately, I received the later seal (mid-73 thru 86), which is physically too small. So, updates will have to wait until next weekend.

[Neilk]

I am going to install the seal tomorrow but I wasn't sure where I should place the seal. Can someone indicate where it should go? I edited the mainshaft picture above so I could eliminate any confusion.

Thanks

[Grady Clay]

Neil,

I assume you are talking about the “dam seal “and not the regular input shaft seal. The input shaft seal position is relatively fixed by the machining of the transmission parts.

There are two considerations about the placement of the “dam seal.” First is it must be sufficiently toward the transmission where it doesn’t interfere with the hub of the clutch disc, Second, it must be sufficiently close to the engine where any oil leakage will drip (or spun off) the input shaft and go out the drain hole.

That is where we made the installation tool.

Best,
Grady

[ChrisBennet]

[Neilk]

Yeah, I was talking about the dam seal. I guess somewhere between the first and second lines on the left should work. I will make sure that it doesn't get anywhere near the clutch hub.

Thanks again,

[ChrisBennet]

Ooops, sorry. I had another Senior Moment there.
-Chris

[Jim Richards]

Either that or the Lime Rock trauma was more severe than previously diagnosed, Chris.

I will probably finish this next weekend or the weekend after that. Overcome by events.

[dweymer]

Jim, Grady, or anyone:

Did you ever get a measurement on how deep the dam seal should seat?

[RWebb]

It turns out that a 1975 trans. needs a different dam seal - the OD has to be 25 mm.

I spent about 2 weeks trying to find the correct sized damn seal...

On the bright side, I was able to install it using a piece of pipe commonly used for household plumbing.



The same metal pipe serves to protect the drill bit from nicking the input shaft. The hole needed to be drilled way back inside the bell housing, so I had to use a right angle attachment on the drill, and to get it started I used a cutoff tool on a Dremel to make an "X" in the surface of the guide tube.



This pic below shows tape over the input shaft splines to protect them, and a piece of wood (artist's brush) stuck in the drilled hole to keep me from pushing the seal in too far.



The trans. is upside down in both pics, and the guide tube is smeared with rust reducer in an attempt to get rid of rust.

[kwikt 911]

I did the ol dam seal trick on my 72 915 tranny last summer along with a new seal of course. So far no leaks

Kevin