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Old 05-16-2017, 11:13 PM   #1
bmw-slangen
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Default Getrag 260 is leaking - but why?

I have a very strange gearbox leakage and really need expertise help!

It is a E30 323i -85 with a standard manual Getrag 260/5 gearbox.

When I drive hard on the track, it starts leaking quite badly from inside the bellhousing.

But when driving "normal" it doesn't leak at all.


I'm really hoping that someone else recognize this problem and can help me!




--- Here is some more in-depth but important details ---

I can drive "normal" without any issues.
The problem occurs when driving hard on the track.
The first stint (20 min of hard driving) is usually not a problem.
Halfway through the second stint (usually you rest for 20 min between stints), it starts to leak really bad.

I tried with the original gearbox two times and then I also tried with a spare gearbox - same result.

It is 100% confirmed it is gearbox oil and not engine oil or brake fluid.
It is 100% confirmed it is coming from within the bellhousing.

I verified the vent hole is not clogged (goes for both gearboxes).

I use ordinary ATF "Dexron III" transmission oil (goes for both gearboxes).

I verified the fill level is according to specifications (goes for both gearboxes).
Means that I fill up to the fill plug level with the car level.

On all occasions it's been basically bone dry around the vent hole (so nothing comes out from that one).

On the original gearbox I
- replaced the input shaft seal TWICE (part #9)
- replaced the sealant of the housing cover and the screws TWICE (part #6 and #7)
- made sure every time that the housing cover was oriented properly to the oil passage
http://www.realoem.com/bmw/enUS/show...diagId=23_0579

On the spare gearbox I
- replaced the input shaft seal (part #9)
- replaced the sealant of the housing cover and the screws (part #6 and #7)
- made sure that the housing cover was oriented properly to the oil passage
http://www.realoem.com/bmw/enUS/show...diagId=23_0579

On the spare gearbox I
- sealed (from the outside using RTV) around the layshaft bearing visible in the bellhousing (part #24, #21 and #22)
http://www.realoem.com/bmw/enUS/show...diagId=23_0144

I pressure tested (around 1 bar) the spare gearbox and nothing...
Not the slighest indication of a leak (checked by listening as well with soapy water)...

Last edited by bmw-slangen : 05-18-2017 at 03:56 PM.
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Old 05-17-2017, 06:47 AM   #2
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wow, that's crazy. maybe the fluid is just expanding so much from the heat of hard driving?

pressure test with a higher pressure. it sounds like its coming from where you rtv'd
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Old 05-17-2017, 07:46 AM   #3
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Two gear boxes and same issue. Likely isn't the gear box. On normal driving, the leak probably is just burning off.

Your m20 is known to leak on the back of the head from the valve cover gasket so I would start there. Could be rear main seal. Could be back of the head gasket. But that's all in order of most likely to least.
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Old 06-12-2017, 12:41 AM   #4
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Appreciate all feedback!


Expanding Fluid : I have been thinking about this one as well - but rejected it quite quickly.
Let's assume it is expanding, where would it go then?
Through the vent hole.
But it is bone dry around that one (and all the areas around it).
So nothing comes out from the vent hole - that is a fact.
And even if it did, it's pretty hard to explain how all that fluid is magically transfered into the bellhousing and up onto the input shaft - without leaving a trace :-)
-- So this can be ruled out ---



Higher Pressure Test : Will not reveal more than it did.
If nothing is leaking out at 1 bar above atmosphere, then nothing would leak out at 0 bar above atmoshphere.
When operating, the gearbox will NEVER be pressurized - it will have atmostpheric pressure. There will be NO pressure inside the gearbox.
This since the vent hole is fully functional - there will never be a pressure build up inside the gearbox.
The pressure test was simply used as a tool to find any potential hard to find cracks, leaks or similar.
--- So this one can be ruled out ---



Normal Driving : To be burnt off, it has to reach the exhaust pipes first.
But it is bone dry on the entire gearbox (and there are no drops of fluid coming out from bellhousing).
After normal road test, I do remove the lower gearbox support bracket,
then I can feel into the bellhousing if there is any oil at the bottom of the bellhousing (and it wasn't).
If it was burnt off, it had to come from somewhere. And there is nothing. Anywhere.
Remember this is a track day car, so after a road test drive,
it is quite common I jack up the car up and do an extensive visual inspection of the entire underside.
I know that underside inside and out by now :-)
--- So this one can be ruled out ---



Leaking M20 : This can easily by ruled out.
My engine oil hasn't got a cherry red colour :-)
The gearbox is the ONLY thing on the entire car holding cherry red ATF oil!
I didn't mention it (since it's not engine oil that is leaking) and of course impossible for you to know it,
but when it comes to engine oil leakage there are currently no issues.
But it didn't come for free! Trust me one this one! This one I'm in full control of.
Due to various reasons, a complete visual inspection of the ENTIRE engine area has been done,
roughly around every 3rd hour of engine operation.
So basically not a single new drop of engine oil can form without me knowing about it :-)
--- So this one can be ruled out ---



As you can hear, I'm quite frustrated - especially since the track day events are here now and I don't have a car that I can drive.


Here is a shot that shows how it looked like from the last track day I did.


Last edited by bmw-slangen : 06-12-2017 at 12:44 AM.
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Old 06-12-2017, 08:52 AM   #5
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Have you been swapping the same Clutch master from trans to trans? In the pic that area appears to be the wettest and if you have a bad clutch master seal the amount, and aggressiveness of shifting in an on track environment could be causing it to leak, where normal driving may not be enough to cause noticeable leakage.
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Old 06-12-2017, 09:50 PM   #6
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I think there's a cover on the top where the gasket is usually destroyed.
Perhaps that is leaking.

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Old 07-01-2017, 05:08 PM   #7
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the cover actually warps causing the most misdiagnosed tranny leak , bmw even had a bulletin about it . most replace the shift shaft and output seals thinking thats the cause only to find its the shift detent cover is the real source . and there's no gasket ,just anaerobic sealer so it is critical that the cover is flat
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Old 07-01-2017, 05:32 PM   #8
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Damn, I missed to update in this forum (managed to remember the other ones at least)!

Short story : It came from the vent hole.

But so far I haven't heard anything explaining why or showed why (heard about overfill, heat expansion and so on).

But I actually reproduced the problem, under what circumstances it happens and everything on film.




Ok, let's get straight to the point - I was wrong and you were on the right track!

The problem was due to overflow from the vent hole!
But not due to expansion, foaming or wrong gearbox oil and so on.


I wanted to recreate the problem, so I had the gearbox on the bench, filled to specified level and was running the input shaft with a drill.

With the gearbox completely level, nothing happened. Not a single drop.

But then I tilted the gearbox 45 degrees to simulate heavy breaking, while the input shaft was spinning.

And now it basically was pouring out gearbox oil from the vent hole!

https://www.youtube.com/watch?v=LbVn3-wNsG0



So the solution was to attach a hose (using an ordinary hose clamp) to the vent hole, and it was then routed up as high as possible in the engine compartment, with a small breather filter at the end.

When you had the gearbox tilted down it was quite easy to attach a hose, and then secure it with a hose clamp (I tried and couldn't even pull it off). But with the gearbox in it's installed position I declare it IMPOSSIBLE to get to that vent hole!



So I was wrenching like cray from 06.00 to 21.00 entire Friday to get the car ready for the track day the very next day.

Up at 05.30 on Saturday and away to Ljungbyhed (a former military airfield) - and success!

I could put in lap after lap without a single problem!

https://www.youtube.com/watch?v=_z0_jcdsd8k



You got me thinking twice what I did wrong in my thinking and my assumptions and basically revisited and went through everything from a fresh point of view.

I still can't get over how bad I could misjudge the evidence in front of me.
But I should have known better - I know that oil in turbulent air flow can do basically anything!

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Old 07-02-2017, 10:10 AM   #9
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Bad ass deal that you got it. Funny how it was happening, though. You really have to stomp on the brakes to put it up to get that leak
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Old 07-02-2017, 10:32 AM   #10
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Yeah, quite interesting. Notice that it doesn't leak at very low revs (or no revs at all). So it's not that it is leaking it by itself. You need to build up some revs to push up the oil through the vent hole. Whenever I have the chance to "dissect" a Getrag 260/5 I will actually have a close look on that.


R compound tyres (Kumho Ecsta V70A), Corvette C5 brake discs, BMW M3 E36 brake calipers and race brake pads (Carbotech XP8) does a quite good job slowing down that 1050 kg "heavy" E30 :-)
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