915 Transmission input guide tube leak?

[Tom '74 911]

Hi -
I have a '74 911 w/a '74 915 (I believe) and a '77 2.7. I just successfully dropped my motor and trans. for the first time a few days ago (maybe I'll start another thread on that) and finally separated them this evening to find. . . some swepco fluid in the throw-out bearing. My clutch seemed OK before winter hit and I parked it, but I will certainly do some further inspecting.

So do I have to fully tear the transmission down to fix this leak? I did some searching and found some photos of other 915 guide tubes that looked like they were accessible from the outside, but mine doesn't. Help!

Thanks,
Tom

[MBEngineering]

HI Tom
you may just be lucky with your box, if you get the new seal and try it in the end of the tube and if it fits it, you can replace without a strip, check the depth of the old seal and see if you can hook it out, if poss'( if not push it into the box and fit the new one) you will have to make a tube to fit the new seal into the box at the correct length/depth. Remove the diff side plate and the diff, then cut the old seal from the input shaft, refit the diff and side plate (with a new seal) job sorted.
Tool something like this;





you will need to drill a long way in as to go over the input shaft.


sorry about the photos , hope it helps.

regards mike

[javadog]

Tom,

Your gearbox is probably earlier than '74. I think the design changed to the easily removeable seal sometime during 1973. The numbers on the transmission case should tell us that. There has been a lot of discussion on this board about these early seals. Yes, they are replaced from inside. There have been a couple other things that have been done in addtions to the seal replacement. The housing can be modified to make the seal relpaceable from the outside next time and a second "dam seal" can be added to keep oil off the clutch if the shaft seal leaks in the future.

Look at this thread to start with, then do a search and read some of the others. This has been discussed quite often and there is a lot of good information out there.

Go here: Input shaft seal Problem with 915 Mag case

JR

[Tom '74 911]

Originally Posted by MBEngineering

HI Tom
you may just be lucky with your box, if you get the new seal and try it in the end of the tube and if it fits it, you can replace without a strip, check the depth of the old seal and see if you can hook it out, if poss'( if not push it into the box and fit the new one) you will have to make a tube to fit the new seal into the box at the correct length/depth. Remove the diff side plate and the diff, then cut the old seal from the input shaft, refit the diff and side plate (with a new seal) job sorted.

sorry about the photos , hope it helps.

regards mike

Mike -
Thanks for the info. I'm glad it may be possible, but am not sure about being able to make a tool that would work like the one in your photo - thank you for that by the way, photos are great! I understand the process at least now. Is the success rate about the same for replacing the seal from the outside vs. from the inside?

Thanks,
Tom

[Tom '74 911]

Originally Posted by javadog

Tom,

Your gearbox is probably earlier than '74. I think the design changed to the easily removeable seal sometime during 1973. The numbers on the transmission case should tell us that. There has been a lot of discussion on this board about these early seals. Yes, they are replaced from inside. There have been a couple other things that have been done in addtions to the seal replacement. The housing can be modified to make the seal relpaceable from the outside next time and a second "dam seal" can be added to keep oil off the clutch if the shaft seal leaks in the future.

Look at this thread to start with, then do a search and read some of the others. This has been discussed quite often and there is a lot of good information out there.

Go here: Input shaft seal Problem with 915 Mag case

JR

JR -
Thanks for the link, I did not come across that one in my searching. The number on the bottom of my trans. is: 915-06-7349176 which I think is a '74. Wevo's guide tube upgrade looks interesting as well.

EDIT:
Here's some info from the tech. specs. that list it as a '74:

TR003
EXPLANATION OF THE TRANSMISSION-NUMBERS USED IN THE CATALOGUE
================================================== ===========

DIGIT: 1 2 3 4 5 6 7

EXAMPLE: 7 2 7 0 3 5 5
= = = =======
! ! ! !
TRANSMISSION TYPE---------------------------------+ ! ! !
! ! !
TRANSMISSION VERSION--------------------------------+ ! !
! !
MODEL YEAR--------------------------------------------+ !
!
SERIAL NUMBER------------------------------------------------+



GR001
TRANSM. TECHNICAL
VEHICLE TYPE TYPE MJ TRANSMISSION NO. DATA
911/911S/CARRERA 915.16 74 4 724 0001>> 4-SPEED
911/911S/CARRERA 915.06 74 4 734 0001>> 5-SPEED
911/911S/CARRERA SPM 925.02 74 4 764 0001>> 4-SPEED

[Tom '74 911]

Hello again -
An update . . . . .
From the outside, I was able to pull the old seal out and get a new one in - although I can't say for certain that it's final resting place was where it really was supposed to be. I cleaned the input shaft and guide tube fairly well before installing the new seal.

Fast forward to today - after driving since May or so, w/a few track days thrown in, it's started to leak again. This time it looks to be a bit more serious - not terminal, but more than just a few drops of blue swepco on my garage floor. This afternoon I started prepping to drop the engine and trans. to inspect the situation further. I'm planning to install a new seal again and look the clutch disk over to see how contaminated it is.

Some questions - can someone tell me exactly how far in the seal should be installed? I'm wondering if I didn't get it in far enough. Also, do any of you ever put any kind of sealant around the outside of the seal? I read in another thread about 3-bond 1104, but also ran across many others that warned against it.

The transmission seems to be in generally good shape other than this leak. It shifts well and I really have no other gripes. If I have to tear into it, I'd feel obligated to go through the entire thing and do a few upgrades - which my bank account would love to be able to put off for a while!

So, for the guide tube that I've got (the non-removable from the outside type) what can I do that will allow me to get through the rest of the summer - longer would be even better - w/out opening it up?

Thanks a lot,
Tom

[jkh2cpu]

Question: how much trans oil are you putting into the transmission? Porsche says about three quarts (it will take four and blow the seal). As I recall, the manual says to check the level by putting your finger into the filler hole and feeling for the level of the fluid, which should be around 1/2 inch below the filler hole.

HTH.

John.

[Tom '74 911]

Originally Posted by jkh2cpu

Question: how much trans oil are you putting into the transmission? Porsche says about three quarts (it will take four and blow the seal). As I recall, the manual says to check the level by putting your finger into the filler hole and feeling for the level of the fluid, which should be around 1/2 inch below the filler hole.

HTH.

John.

Hi John -
It has always leaked a bit from there I think, since I got the car. I initially assumed it was oil from the engine, but when I dropped the motor this past winter, I found swepco in the throwout bearing - hence this thread!

It is a possibility I suppose - that it came to me a few years ago overfilled and that I over filled it when I changed out the swepco last year. I filled it until it just barely started to overflow out the filler hole. I will check to see where the level is now before I drop it for another seal swap.

Thanks,
Tom

[Fast Corners]

Tom,

While your tranny is a '74 unit the guide tube type is the earlier style ('72-'73). Porsche often used earlier parts on later cars until stock supplies were used up.

The guide tube on your transmission needs to be removed from the housing inorder to properly install the seal. I replaced the one on my '73 back in the early 90's. I know that I replaced mine without disassembling the tranny case. While I do not remenber the particulars I do recall that it was easier than I imagined. I'll look at my spare tranny tonight to see if I remember how I did it.

IIRC, the seal is installed from the back side of the guide tube (the end that is in the tranny case) and should be set flush with that end of the guide tube. You need to use extra care when installing the guide tube & seal assembly back over the splined shaft as the splines can cut the sealing surface of the seal. There are many methods for doing this but the best one I have seen is to wrap the splines with a thin layer of electrical tape (front to back so the seal will slide better) and then coat the tape with a thin layer of tranny oil. Work the tube w/ seal carefully over the shaft making sure the seal lip is positioned properly (pointing back towards the Ring Gear). You may need to work the tube back & forth or use a wood or plastic tool to push the lip back. Once the seal is good all you need to do is press or tap the guide tube home. Use a soft wood block so as to not damage the tube.

BTW, any leak of transmission fluid in the bell housing can be a potential bad day. If the clutch disk gets soaked enough, not only can it's effectiveness be reduced but it can detonate (fly apart with a loud bang) at higher revs. I've been in a car (instructor) when it has happened. This effectivily leaves you without a clutch.

Good luck & keep us posted.

[Peter Zimmermann]

Tom: Your TOB guide tube is correct for a '74 car. Removable guide tubes didn't come until later. You should have a P 386 (puller) for seal removal. To install the replacement seal you need P 382 (sleeve) and P 381 (driver). 382 slides over the splines and prevents the sealing lip of the seal from being cut during installation. 381 is used to install the seal to: (1) the correct depth, and (2) perpendicular to the mainshaft (necessary because if a seal is crooked it turns into a screw). If you can't find a 382 you can put a couple of layers of electrical tape around the splines to protect the seal. If you can find someone with a 381 have them measure the depth for you (I don't have these tools, they were left at the shop), perhaps you can rig up a piece of pipe with a hose clamp on it to act as a stop.

[Tom '74 911]

FC & Peter Z. -
Thanks for the comments. I do plan to inspect my clutch disc once accessible to see if it's contaminated. It'd be a shame if it is because it was brand new 3 months ago!

I've been reading through the factory manual and ran across the same tool numbers as well as a description regarding pulling and installing a new seal. Last winter, I was able to remove the old seal by (carefully) screwing some screws into it and pulling it out - don't yell at me for my archaic methods! I used a piece of nicely sized pipe to install the new seal but didn't protect it from the splines and probably didn't install it to the correct depth. I feel like it was fairly perpendicular to the shaft.

So I guess my remaining questions are:
1. Can someone who has access to tool # 381 measure the depth for me?
2. Answer the question regarding putting some sort of sealant around the outside lip of the seal for insurance? I'd rather be driving than fixing!

Another question too - would it be worth removing the final drive side cover to have a look inside as I'm installing the seal? If I do remove the cover it looks like the axel flange shaft must come off first. If I take these two pieces off will I: (1) be able to see the inside of the guide tube and will that help me, and (2) will I likely knock anything out of adjustment that will need recalibrating when I put it back together? I definitely don't want to make more work for myself if it's unnecessary.

Thanks a lot for the help,
Tom

[RWebb]

I think Wevo makes a fix for the non-removable guide tubes. Pelicn prob. carries it.

re [1] you'd have to remove the R&P also I think

[2] IIRC< this can be done w/o having to reset anything really expensive

search on my name and trans* to get info on trans upgrades year by year and what I did re my guide tube.

[Peter Zimmermann]

Originally Posted by Tom '74 911

So I guess my remaining questions are:
1. Can someone who has access to tool # 381 measure the depth for me?
2. Answer the question regarding putting some sort of sealant around the outside lip of the seal for insurance? I'd rather be driving than fixing!

Another question too - would it be worth removing the final drive side cover to have a look inside as I'm installing the seal? If I do remove the cover it looks like the axel flange shaft must come off first. If I take these two pieces off will I: (1) be able to see the inside of the guide tube and will that help me, and (2) will I likely knock anything out of adjustment that will need recalibrating when I put it back together? I definitely don't want to make more work for myself if it's unnecessary.

If the seal is clean & dry, and the inside of the tube is clean, dry and free of any oil (use Q-Tips and lacquer thinner for this) you could probably put a thin coat of Curil T on the OD of the seal. I use a light smear of white lithium grease on the sealing lip as well.

Don't worry about opening up the diff, it's a lot of work and won't help you. Once you have the correct depth of the seal you can set up a driver - just be sure to tape those splines! To double check depth use something to measure from the end of the guide tube to the beginning of the M/S sealing surface (it's raised), then add 5-6mm - that will definitely get you in the ball park. Be sure to factor in the offset of the seal's sealing lip!

I will try to call someone tomorrow and have them measure the tool for you. If I get an answer I'll post it tomorrow!

[Tom '74 911]

Originally Posted by RWebb

I think Wevo makes a fix for the non-removable guide tubes. Pelicn prob. carries it.

search on my name and trans* to get info on trans upgrades year by year and what I did re my guide tube.

I have heard of the Wevo fix - I think it requires machining the case though.

I did some more searching and found this excellent thread:
Input shaft seal Problem with 915 Mag case

Which has this photo that really shows the input shaft and where the seal should go.



That photo and Peter's post above will help me visualize how to measure how deep the seal should be pressed in. I really appreciate everyone's help!

Thanks a lot,
Tom

[Tom '74 911]

One more quick question - I plan to follow RWebb's procedure in the thread I posted above to drill a weep hole in the guide tube and install a dam seal. Is there any reason that using a separate input shaft seal wouldn't work as the dam seal? It seems like sourcing a separate seal that would work is a difficult prospect.

Thanks,
Tom

[Fast Corners]

Tom,

Interesting thread you found there. It seems to me that the dam seal can be any seal that fits over the input shaft. I would be sure that the one you use does not contact the shaft though.

[RWebb]

cheapest tool is plumbing pipe - plastic is fine for the 'pusher'

be sure to use metal for the protector as you do NOT want even the smallest drill bit nick on the input shaft - it will create a stress riser

dunno if Wevo's fix requires machining or not; if lucky the entire diff & case could prob. be replaced with a '77 or later

glad my pics could help you.

[Peter Zimmermann]

Tom: The depth of your mainshaft seal, based on the dimension of P-381, is 40mm.

[Tom '74 911]

Originally Posted by Peter Zimmermann

Tom: The depth of your mainshaft seal, based on the dimension of P-381, is 40mm.

Peter -
Thanks so much for your help and research - I appreciate it.
Tom

[Tom '74 911]

OK -
Some progress. I pulled the engine/trans. and got them separated this afternoon. Here's what I found:










Basically, exactly what I thought it might look like. I measured how deep the input shaft seal was installed - 45mm. Could I have installed it backwards? The side w/the lettering was facing out - towards the engine. Is that correct? When I installed it a few months ago, I didn't wrap the splines of the input shaft w/tape - something that I'll do this time for sure.

Finally, is there any way to tell for certain if my 3 month old clutch disk is too contaminated? I'm assuming it is, but it'd be nice to be able to save it (and the $211). It's not dripping in trans. fluid obviously, but??? I included a photo of the flywheel in case the darker discolored area helps to determine the clutch's condition. I had the flywheel turned a few months ago when I put the new clutch in - it's still super smooth despite the heat marks.

I tried to get the old input shaft seal out to examine it, but only succeeded in pushing inboard too far. So now I get to rig a hook tool to get it out!

Thanks,
Tom