Trans input shaft seal - need expert advise

[Chuck Moreland]

I need to replace the input shaft seal on my trans. It was leaking like a seive, and I suspect much if not all the leak was from the outside of the guide tube - not the seal.

It's a 73.5 and has the early 915 style guide tube, with no screws to secure it. Just a press fit into the trans case.

First question:

From which direction should the seal be inserted into the guide tube.

From the trans side like this:



or from the engine side like this:



Bentley says "from the front". Well that's a bit ambiguous.

Second question:

Do I have the seal oriented properly in the above pictures, or do I have it backwards?

Third question:

There is a small ID section, about 3/8" long near the trans side of the tube. Should the seal be installed inside this small ID, or should the seal be on the trans side of the small ID - using the small ID as a backstop?




Fourth question:

Do I need the special Porsche tool 000 721 381 00 to do this correctly, or can I press it in using a well-selected socket?

Fifth and final question:

The guide tube is not particularly tight in the case (remember it's the press fit variety). In fact when I seperated engine and trans the guide tube went with the engine. I believe this was the root cause of my leak.

I've been advised to use Curil T on the outside of the guide tube to help the "O" ring do its job. Is this going to be adequate hold the guide tube in place? Or should I be buying a new guide tube? or using some more secure sealant?

[Chuck Moreland]

Bada bump

[ischmitz]

Chuck,

I had a couple of input shaft seals on the input shaft when I took my 915 apart. That tells me a P.O. had service performed where the shop simply pressed a new seal into the tube from the outside without opening the box. Seems to be comon practice or so I was told.

Ingo

[Jim Sims]

I did this job with my son's 73.5 T 915 transmission and recently with another '73 915 transmission; I seem to recall we just put the new seal in the way the old one came out (yeah I know, that's not a lot of help). I remember doing the job twice on the first transmission because we damaged the seal. Ultimately both installations were leak tight but then again our guide tubes didn't come out. Let me see if I can find my notes....

[Jim Sims]

The factory shop manual shows it being installed from the transmission side (from within the final drive housing) and states the sealing lip should face toward the bell housing (toward the engine). I remember this, as it seemed backwards to the way seal lips are usually installed. We used a piece of 1-1/2" PVC pipe and our hydraulic shop press to push to seal into place against the slight edge shown in your images; we marked the PVC pipe with the correct driving depth as it is easy to over drive the seal onto the lip and tear up the OD of the seal.

[Chuck Moreland]

Thanks for all the input.

After sleeping on it and looking with less-tired eyes this AM, I think there is only one reasonable way for this to go together.



Picture above shows the direction of rotation of the input shaft. Notice the seal has those little angled wipers. The angle must be arranged such that the rotation of the shaft sheds oil back into the trans. So the orientation of the seal must be correct in the picture.

Onto that small ID section.

The seal is simply too small to fit tightly into the guide tube, except at the small ID section. I note the width of the small ID corresponds closely to the width of the seal. Like they were made for each other

I used a socket that barely fit into the guide tube along with a bench vice to press the seal into the small ID section.





Above pics show the result. The seal appears square in the bore.

The only remaining question is fitment of the guide tube into the case. Is the Curil T going to do the job of sealing and securing the not-so-snug guide tube to case fit. And will it do the job too well, preventing future removal of the guide tube?

[CliffBrown]

Chuck

I'm going to point out one suggestion and I'm going to assume that you've already done this.

Make sure that when you refit the guide tube that the seal is surrounding the raised sealing surface of the input shaft. You might need to move the seal in or out depending.

[ischmitz]

and don't forget to lube it (or the input shaft). Otherwise it'll get torn up right away.

[Chuck Moreland]

The Curil T didn't do it. Several hours of cure time and it still pulled right out.

Surely the guide tube is not supposed to be this loose. I'm thinking loctite blue.

Any bright ideas.

[CliffBrown]

Chuck

This isn't a sugestion but a JB Weld type product is used in a few locations on our 911 motors.

[Chuck Moreland]

I'm trying to work a balance between keeping the tube in place, and being able to remove it should that be required in the future.

one thought is to pinch the tube in a vice just a bit such that it will fit more tightly, yet the case will make it round again once installed.

[1fastredsc]

If it's a press fit your worried about, you can use locktite green, which is for press fit sleeves.
EDIT: It might be permatex green, i get the two confused sometimes.

[84toy]

Hey Chuck, a good way to remember seal directions is by the spring wrapped around the lip of the seal. The spring goes towards the direction of the fluid you are trying to contain. In this instance, it's tranny fluid so the spring side aims towards the tranny, not the engine.. Have fun....

When I use a double lip seal like the one shown, I wipe a little grease between the two lips. (not a lot because of the clutch) This lubricates the outer lip of the seal

[BURN-BROS]

Chuck,

Try "Pro Lock" part # 81797

press fit assist

I have used it on damaged shafts when a bearing spins on some equipment. Good Luck!