Name that Leak - Please? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

I've been struggling with fluid leaking from my car since not long after I got it back from the shop. The patient is a 2004 S 6-Speed Transmission was rebuilt by G Box less than 5000 miles ago IMS, RMS, Flywheel and Clutch replaced by a very reputable shop 500 miles ago 200 miles ago I started noticing drips on my garage floor. Cleaned her up real good and it became clear that the leak was coming from the bell housing. Joe Gibbs DT 40 and the Porsche transmission fluid smell a lot like each other and have the same yellowish color when new - compared them bottle to bottle. So I got myself a 4 post lift and a transmission stand. Pulled the tranny and here's what I found: Fluid pooling in the bell housing Behind the flywheel appears to be dry. Is there an obvious diagnosis or should I proceed to pulling the clutch and the flywheel? What say you experts who are smarter than I? Thanks for the help!

...and on further inspection, the inside of the bell housing is coated with an oily substance....if that helps. Thanks!

I wonder if the throwout bearing guide collar inner seal was replaced? I would think G-Box would have done that. Have you talked to them ?

Just pulled the tranny today. I'll look at my receipt from gbox. Thanks!

just checked my gbox receipt. There are actually 2,500 miles on this rebuild that included the os-Giken lsd. The following seals were replaced: main shaft seal, differential side seal and shift arm seal.

Just spoke to GBox. They were very helpful. I was told that replacing the input shaft seal is pretty straightforward - pick the old one out - tap the new one in - just not too far or it will fall into the transmission. Does this sound about right to everyone? Any pointers?

GBox needs to give you the tech advice on this, not us ! For example, you need to examine the input shaft for wear/marking where the lip of the seal fits.If there is any discernible marking ,discuss with GBox because fitting a new seal may be futile. If the marking is slight, can it be 'improved' ? If it can, is it possible to fit the new seal to a slightly different depth ? GBox to advise. Similar issues arise with the RMS and sometimes experts(not me) suggest setting the new seal to a different depth to avoid repeat leak problems. Let us know what happens?

You're right, I'll be in touch with them again. The guy on the phone did not seem concerned at all. He just told me to get a new seal, pick the old seal out with some picks and tap the new one back in. There is a lip where it is supposed to stop and if you tap the new seal past the lip, it falls into the tranny. You're right though - why did it fail in the first place, only 2500 miles since the rebuild? This can't be a very common problem since I have rarely found this issue mentioned in the forums.

Well, it was definitely the input shaft seal leaking. Gbox was equally puzzled by this but helpful and responsive over the phone. They requested that I confirm it was for sure not crankcase oil and that my pilot bearing was not seized or missing. I pulled the clutch and flywheel - both nearly brand new and in good working order. The RMS and IMS were both dry. I did install a new pilot bearing just to eliminate that as a possibility. I pulled the main shaft seal of the transmission to find that it was definitely leaking. Interestingly, it was not an OEM part. Comparing the 2 seals side by side, the OEM Porsche part was clearly more robust and had more surface sealing area. I would have expected that a high end company like GBox would have used OEM seals, and perhaps seal failure is really the root cause here. Then again, only time will tell... Here's a picture of the 2 seals side by side (The non-OEM seal is damaged due to removal)

Were you just unlucky and got the wrong sub-spec generic seal ? A one-off problem -lets hope. Or are all the recent GBox 6 speed transmission rebuilds going to fail because of this seal ? Can you Post the exact markings from the correct seal so we know what to check for? If you can also give me the markings from the failed seal ,I can research and try to give a comparison of the two specifications.

The seal is marked 111801 28 40 8R 8 SOG It looks exactly like this one: 2004 Porsche Boxster S Convertible - Transmission - Page 2 The OEM Porsche Part that I got from the dealer is: 996 301 805 00 There is quite the difference in cost between these 2 - the OEM is 3x the cost - but the photos don't do it justice as the OEM is clearly just a much more robust part.

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This is the same thing I found when I changed the output shaft seals on my trans. I ordered the OEM part from Pelican, but when I pulled the existing seal it was clearly a much better part. I then ordered the Porsche seals from Pelican. More money but a much better part.

Looks like that us just a generic seal ; Also fitted to Mitsubishi. I found generics for $3.This one is branded for $9 MITSUBISHI ENGINE OIL SEAL 28*40*8 R mm NJ 373 Here are some SKF with higher temperature material: https://www.motionindustries.com/productCatalogSearch.jsp?q=28+X+40+X+10++++MM+A-NBR+SEAL My personal rules with seals and bearings is to buy the best/most expensive: https://www.motionindustries.com/productDetail.jsp?sku=00611488 Because the R&R costs 100X that of the generic seal price. ASk California MotorSports,GTGears, or "Erick"to comment.They are much smarter than me on this issue.

Admittedly, I'm a bit disappointed with GBox for using an inferior part in my rebuild. There's no excuse for having to pull a leaking tranny after 2500 miles.

Hey it could have been worse: 1. the oil loss could have ruined the new (?) bearings that GBox fitted, 2. the leaking oil could have saturated and ruined the clutch friction plate, 3. you may have confused it with leaking RMS or IMS and replaced them needlessly 4. you may have had to pay an Indie to R&R the box and ship it back to GBox. This could have been a hugely expensive mistake for both you and GBox. Fortunately ,you did all the work to diagnose and fix the problem and all the R&R .I hope they express their gratitude to you in an appropriate manner. To be fair, the seal may be adequate spec.It may have been a defective seal, seal damaged during installation, gearbox overheated during use/abuse........ I wonder if GBox will contact other customers/Forum members with the same seal to alert them?

Hello, the OEM seal has these fine grooves. The after market one on the photos not. Besides material quality this difference in design makes a big difference in how good it can seal. Regards, Markus