Replacing 901 Tranny Shift Shaft Seal

[rw7810]

Just how to you go about changing this little sucker?? Got the trasnny out while rebuilding engine. Thought I might as well change the tranny seals. Got all of the rest out, but the shifter shaft in another matter. Any insight??

[svandamme]

i did mine two weeks ago on my 915
very difficult to pry it out

i tried screwing in a screw , then pull on the screw , didn't work
in the end, it took lot's of cursing , and a sharp set of plyers

the old seal will most likely come apart at some point, just make sure no leftovers are in there when you install the new one...

i've heard people saying it can be done with tranny in the car, but i fail to see how that would work... them shaft seals are tough cookies

[Grady Clay]

Bob,

The best way is to remove the nose piece but you possibly can pull the seal with the shift rod in place.

Do not damage the sealing surface of the shift shaft.
Do not damage the bore where the seal sits in the casting.
Carefully inspect and dress any burrs on the shift shaft, particularly at the shift connection.

There are good commercial pullers available. A reasonable DIY solution is to use a long (4”) but thin (#6 or smaller) deck screw. You need some brass shim stock to protect the shaft from the screw. Make yourself a “slap hammer” puller from a long bolt and something heavy. Slide the shim stock past the seal as far as it will go. Screw the deck screw into the seal. The seal is usually a combination of steel and rubber. You probably will have to try several locations around the seal.
Many have been glued in place or are firmly in place from age or corrosion. In that case you need to pull the nose piece.

Stijn is correct, it's a PITA. I recomend pulling the nose piece.

Best,
Grady

[Jim Chambers]

Lets hear more on this. I have to do it next week.

edit: are we talking main shaft seal or something else? My job is the main shaft seal.

[svandamme]

the main shaft , do you mean where the axles bolt on ?
those are relatively easy , they come out pretty nice..

the shifter rod seal is a lot more difficult , because of the small diameter
it doesn't budge because it's too small to deform

[Jim Chambers]

I am talking about the seal around the shaft which goes through and is driven by the clutch disc. To me that is the main shaft.

[svandamme]

ah , dunno bout that one... haven't touched mine yet

[rw7810]

Yes, since it's out, I think I'll just pull the nose. I used the screw technique on the input shaft. Thanks Grady and Stijn

[SpeedracerIndy]

I had no trouble pulling my shift shaft seal. Pried it out with very little force and popped the new one in just the same, guess I was lucky. As others said, just be careful not to score the housing when you pry it out. For the main shaft seal on the other end of the tranny you unscrew the two phillips screws holding the throw-out bearing guide sleeve in place, then thread a coat hanger (or something similar) through the two holes on the end of the sleeve and pull it out with the coat hanger (and a good amount of force). Pretty simple. You don't want to pry on the throw out bearing guide sleeve because you can deform it, that is why there are two holes provided on it to yank it STRAIGHT out. Then on the work bench you can remove and replace the main shaft seal, and then reinstall the throw out bearing guide sleeve and you're done.

[Grady Clay]

Bob,

You need to read this thread:
Transmission input shaft oil seal on a 69 what's involved in replacing?

Best,
Grady

[SpeedracerIndy]

That is a very helpfull thread Grady! I wish I had read that before I put mine all back together. Very good idea about cutting a groove in the throw out bearing guide tube to prevent the clutch from getting oil soaked.

Does the 901 not have the two holes in the throw out bearing guide tube to pull it out of the tranny? I don't know how I would have gotten mine out without those holes in there. It was really crudded in there.

[barlowdo]

I did mine while trans was still in the car. But .... with engine and trans slid back. SO sort of a partial engine out.

I could not see anyway in ____ to do it with out sliding engine and tran back.

Just too tight an area in there.

This was on a 1966 911.

The old seal did not come out too hard once I got so I could get to it.

It sure can cause the tran fluid to drop fast when it leaks !

I think there are other links on this board about how to do a partial engine pull so I won't go into it.

-Don B

[Grady Clay]

CD,

An SC 915 has an O-ring on the guide tube where the earlier guide
tube just bolted up flat on top of the input shaft seal.

What prompted the development of this secondary seal/dam was
the dumb placement of the ’72 915 seal.
In the ’72 we drilled a drain hole in the casting.
Porsche makes great cars but they occasionally make some mistakes.

This “solution” is applicable to almost all ’89 and earlier 911s and some later.
The two critical aspects of this are the drain (groove, hole, drain tube, etc.) and the “dam.”
The dam should be closer to the clutch than the end of the
input shaft sealing surface, but not so close that the hub of the disc can touch it.
Any oil that is on the input shaft will be slung off at the transition from the
sealing surface because the shaft diameter decreases at that point.

Note, the dam does not contact the input shaft.

Something I have never done is to put a small tube at the drain grove or
hole and measure the relative air pressure.
I’m concerned the pressure at the center of the disc is so low the air
flow could carry some leaking trans oil to the disc.





Best,
Grady

[RWebb]

I have been having a hell of time with the damn seal. This town has 250,000 people yet it seems impossible to find the correct sized seal (OD needs to be about 35 mm on a 1975 trans., as Porsche apparently changed the size of the guide tube periodically. I've now spent almost a week searching for one.

Thought I'd hit pay dirt when I figured out that Mtn. Bike forks use these seals, and a search showed that Marzocchi used 35 mm ones. Unfortunately, all the bike shops want $45 for this $4 or $5 item, and I refuse to do that.

IF anyone knows an easy way to find a reasonably priced 35 mm seal, let me know. I've been to every bearing house in this town.

[RWebb]

I was however able to drill the weep hole for oil. This is not a procedure for the faint of heart, as you can nick the input shaft, which will put a definite and short life span on the entire transmission.

You cannot remove the guide tube without tearing down the entire transmission on the 1975 trannys.

I bought a piece of metal plumbing pipe and inserted it over the input shaft in case the drill bit burst thru the guide tube.

I marked a safe position with a depth gauge and Sharpie marker for the hole, giving it a few mm clearance since I knew I'd have to drill at a slight angle (the right angle drill adapter doesn't fit completely into the restricted space available).

I made the first cut with a cutoff wheel on a Dremel, then used the Dremel at an angle to make a star or X pattern. I did this to prevent the drill bit from wandering all over the place, since I had to hand hold it.

Then I chucked up the el cheapo right angle adapter and the shortest drill bit i had in an approx. 1/8" size and drilled away. I stopped and checked the depth of the hole frequently.




THis will apply to all 915, 1972 - 1975. The early trans. have removable guide tubes and 1976 & on do also.

BTW - in the left foreground, you can see foam on a stick swab that can work well to clean up various things; it is a lot longer than a Q-tip.

[B.STRT Assoc]

I manufactured a shift shaft seal puller, machined to the the size of the shaft. Considered selling it or renting it out to people that might want to use it.

took me 5 mins to extract the seal.

Who has interest?