72 911T 915 tranny

[RickGarlock]

Have a leak in the tranny at the main throw out bearing. Car has been sitting in a garage for over 18 years with out running. Believe seal is dried out. Does anyone have any knowledge on how to fix this leak with out tearing down the transmission. Perhaps using Mazda parts or knowledge of a sealing fluid that can be used? Second question, this 72 911T has a small morelli distributor - I want to do Petronix. Anybody know a part number? Best way to contact me is by phone Rick at 410-852-5794

[Flat6pac]

Marelli on a 72, doesn't sound right.
Bruce

[tharbert]

You need to get your transmission serial number to verify but I think you may have a problem. Look at Grady's post, #9 (sorely missed!) and match up your serial number. That seal cannot be replaced from the outside on the 1972 915. They re-engineered it in mid-73.

[Walt Fricke]

Rick - can we assume that you got this car back to running, and that is when evidence of this leak appeared?

You are sure it is transmission oil, and not engine oil through the crankshaft main seal?

Mazda parts? Are some of those the same as Porsche? Less expensive but good quality?

[The cap'n]

A design error in the '72. Gotta come all the way apart. Note the seal is also installed backwards. As for the Marelli, they do, indeed, exist on the 2.4T engines. I worked for a guy that fabricated a kit for Crane to allow their unit to be used in a Marelli distributor, but it never came to market, AFAIK. I've never seen a Pertronix installed in a Marelli, but there may be one out there somewhere. I have issues with the failure rate of their products, so trying to adapt one has never crossed my mind.

The Cap'n

[Eagledriver]

I have a 72. I have replaced this seal without removing the tranny. The best way is to remove the differential and push out the old seal from inside the diff housing. You then drive in the new seal over the input shaft. Lots of caveats here about not letting the seal get damaged by the splines and not driving the seal in too far. The work shop manual has specs for a tool to drive in the seal. I made my own out of PVC tubing.

One could shortcut this process by just pushing the old seal into the differential housing and driving in a new seal in front of it. In theory the old seal would just spin harmlessly on the input shaft inside the housing.

By the way. The seal on my tranny is smaller than the seal listed on pelican parts. The right seal is the same as for a later tranny with the remove able tube. I think the bigger seal is for a 901 tranny.

Give this a try, what have you got to lose?

-Andy

[matt demaria]

Au contraire, Porsche designed the tool for replacement of the seal in the latter half of 1972 when the dealers were complaining and charging for big warrantee times. It is a long tube with a t-handle at one end and a tapered thread at the end which fits into the t-bearing snout. I bought mine from baum tools about 25 years ago. There is also a tube style installation tool. The whole R&I time after engine is out is about 15 minutes.

[The cap'n]

I had and used that tool (sold it at the last Lit Show) and, IIRC, it only worked on the '73s. I could be wrong, but I don't think so. Again, IIRC, the inside diameter of the release bearing guide tube installed in the bell housing section is considerably smaller on the '72s, and the seal sits up against it in the case. The change, which happened in MY '73, made the i.d. larger, and the seal was installed in the tube, rather than in the housing. From that point on, the seal could be pulled through the tube. There's a serial number break that identifies the change. As for dealer complaints regarding warranty times, I worked at a pretty busy dealership in '73, when the '72s would have still been in warranty, and I can't remember a single mainshaft seal leak in a 915 the whole year + I was there., and I worked right next to the 911 unit repair guy in the engine/transmission room. In fact, I don't recall any 915 trans work being done, other than what we did at school.

The Cap'n

[Jon B]

A lot of confusion in this thread.
Unfortunately, Pelican is not always a reliable source for transmission information.

FACTORY WORKSHOP MANUALS DOCUMENT THESE 915 CHANGES

The 915 input seal from '72 to mid-'73 can only be replaced with input shaft removed. Period.

The 915 input seal from mid-'73 through '75 can be removed and installed from outside the transmission, without disassembly. Factory tool P386 pictured below is the easiest way to remove old seal, but there are other ways. DO NOT push the old seal into the transmission and leave it there!

Mid-'73 change occurred at transmission numbers:
915/02....................from 7337375
915/12....................from 7230507
915/08....................from 7830838
Special transmissions from 7931031

From 1976-on, the seal carrier and TOB guide tube was removable, making seal replacement that much easier.

Seal removal tool P386, for mid-'73 through '75 915 transmissions...

[Walt Fricke]

Believe Jon.

For these '72-early '73s you could push or pull the seal out into the differential, and I suppose you could let it dangle from the input shaft.

But there is no way you could get the new seal around the input shaft to push back into the hole. Not even Houdini could manage that. One wonders why Porsche changed from the 901/911 approach to the one they started with on the 915. Maybe the idea that the TOB guide tube, which I think may be inserted as part of the casting process or otherwise permanently installed, could be used as a shoulder to position the seal was alluring to someone who wasn't thinking of servicing? Bean counters?

[Jon B]

Here is a factory diagram of the 1972 915 transmission.

The input shaft oil seal is number 18.
It is installed from inside the transmission, with input shaft removed.
The TOB guide tube opening is too small for a seal to be removed or installed from the outside.
The opening was enlarged in mid-'73 for easier seal replacement.
The TOB guide tube is removable from '76-on, for easiest seal replacement.

[eclipse66]

I had trouble with this seal leaking gear oil onto the clutch disc. I tore it down and gave the case to WEVO to have it modified:

Welcome to Windrush Evolutions - WEVO - Porsche Products

It's a quality fix.