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G50 Input Shaft Seal Leak

I am in the process of changing the tranny fluid in my G50 tranny (with Redline 75W90NS). Once I got the car jacked up, I could see that the bottom of the tranny is caked with grime - no real surprise. Will a known leaky input shaft cause this?

Also, while there seems to be plenty in the archives around replacing the input shaft seal on 915 transmissions, there is surprisingly little info on the G50 version of this job. The closest I found was this thread by Jim Sims asking about the proper seal removal tool. Has anyone done this project recently?

I'd like R&R this seal with the tranny in the car if at all possible. I know that a clutch job is in my future at some point as the tranny sounds like a bag of gravel for the first half-second after I release the clutch in first gear, but I plan to tackle this project incrementally.

Thanks,
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Mark
'88 Carrera GPW Sunroof Coupe
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Old 11-26-2005, 09:52 AM
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Hi Mark,

If you are talking about the shifter shaft seal, I did this on my 87 in situ. Getting it out was not bad - mine fell off. But driving it in was a beatych. I seem to remember using a large deep socket and some leverage.

I don't think the grime would come from the shifter shaft seal as it should be pumping the fluid into the tranny tunnel - unless it is also leaking back out through the end of the tunnel.

Let me know if you any specific questions.

Don
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Old 11-26-2005, 10:30 AM
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Hi Don,

I have a BUNCH of questions, but will try and restrain myself

How did you discover your leaky seal? I saw a couple of drops of tranny fluid on the garage floor and noted in the documentation I got with the car that the mechanic called out a leaky shaft seal but I never saw a record of replacing the seal, so I assume this is still an issue.

Thanks,
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Old 11-26-2005, 10:41 AM
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I figured it out because there was fluid seeping around the plastic drain plugs all up the tunnel - so I opened the access cover and found a sea of tranny fluid.

The G50 definitely benefits from Mobil 1 gear oil. It's also very easy to replace the bushings and ball cup from the shifter. This was well documented in Excellence about 2 years ago.

Don
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Old 11-26-2005, 10:47 AM
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Hmmm, I've had that access panel off before and not noticed fluid in the tunnel, but I suppose I could have missed it. I'll take another look. The tranny may just be low on fluid at this point as the problem was documented 3 years ago (I've only had the car a few months...)....
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Old 11-26-2005, 10:56 AM
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Could be a number of things causing the grime.

>Leaking trans. output flange radial seal(s)?

>Leaking engine crankshaft radial seal?

>Someone overfilled trans. gear oil and it will spill out the vent on top of the trans., then dribble down the sides to the bottom of the trans.?

>Someone bled the clutch slave cylinder and let brake fluid drip down the trans.?

>Leaking trans. input shaft seal?

The best thing to do is clean all that crud off the bottom of the trans. and then you can better diagnose the leak. Since you asked about the input shaft seal............

I've replaced the G50 input shaft seal on two cars. The first time was my own car. It was a struggle like Jim Sims alluded to.

First you have to take the guide tube off. The two screws are usually tight and just a plain screwdriver won't budge them. I encourage you to make sure you use the biggest philips head bit you can fit on the screw. If you try to use the common philips screwdriver size, you'll probably strip out the screw(s) and have to drill the head out. Use a ratchet and screwdriver bit so you can get more leverage. Or use an impact driver. Just be patient.

If you do happen to strip a screw head? Don't worry. Use a drill bit that's the size of the screw head to remove as much of the head as possible. Then you can rock the guide tube back and forth to weaken the leftover head material. This will allow you to either work the screw loose or simply pull the tube over the weakened screw head. I recommend replacing these screws after they're removed. They're soft metal and the philips head is easy to strip out. So save some future headaches by installing new screws.



You can see the one screw that I drilled out in the picture above. Use a pair of pliers to rock the guide tube, padding the jaws with something to keep from gouging the surface of the tube. You do not want to damage the surface of the tube! It must stay smooth or your clutch release bearing will get damaged and you'll have a very stiff clutch pedal.

Once the guide tube is removed, you can get a look at the input shaft seal.



It's tough to get a tool on the seal to remove it. I guess that's why Porsche made the special tool? Both times i've removed the seal, it's been a struggle. The first time was awful. I pushed the seal INTO the transmission!!!! That was a battle to get the seal out of there. What I ended up doing was making some hook tools out of stiff steel rod and pulling like an ox to get the seal out from inside the trans. It was ugly. These hooks won't work on a seal that's still in place where it's supposed to be. The fit is just too tight.

What I did next time to remove the seal, I cut off the handle of a seal removal tool to make it shorter so it would fit inside the bell housing. Just be careful leveraging the tool on the soft metal of the trans. bell housing. Use something to protect the surface of the trans. guide tube bore. Don't worry about damaging the input shaft. It's hardened metal and is VERY strong.



Sorry, but you can't do this job with the trans. in the car. Both the engine and the trans. have to come out. Then you must separate the engine and the trans., to work on the guide tube and input shaft seal.

That gravel/growling noise you hear seems to be typical of the early G50 trans. Has something to do with the clutch pressure plate.
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Old 11-26-2005, 10:57 AM
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Mark - there are definitely two sides to this problem - input shaft versus shifter shaft. Your second post says, "shaft seal". My knowlege is limited to the shifter shaft side of the the tranny.

There's a shift coupler boot that attaches to the tunnel and the tranny - you might look inside this for fluid too.
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Old 11-26-2005, 11:02 AM
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Kevin,

Thanks for all the info. in your post - your descriptions have helped formalize the problem in my mind. You're right - I was referring to the input shaft seal as the shift rod seal (or whatever it's called) and my suspicion is that the PO would have addressed it if it were a cheap, easy fix.

It also seems as though there's more grime on the DS half of the tranny and may well begin around the output shaft seal you refer to.

Thanks again for the tips - that was a great post! I'll clean that thing up real well tomorrow and continue the diagnostic process.
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Old 11-26-2005, 11:12 AM
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Kevin is definitely the expert on this (as well as many other) topics.

I certainly defer to him!
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Old 11-26-2005, 11:29 AM
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You're right about the two facets (at least) of the issue, Don. And it probably explains why I didn't notice any fluid in the tunnel

Is there a fluorescent dye or other marker one can add to tranny fluid to help with the leak diagnosis?

Wouldn't a leak like this (input shaft) cause the clutch to slip? Other than the drips, grime and the "gravel" noise at take off, the clutch/tranny seem to operate normally.

Thanks,
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Old 11-26-2005, 12:27 PM
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