[OTO335i]

Hey guys,

I was putting my winter tires on today and had to also install my oil drain plug cover door back on, while I was underneath there I noticed that there was an oil leak coming down onto the metal cover, I dropped the cover and I could see that my oil leak may be coming down from my oil filter housing and making its way down the intake track.

Anyways, I was looking at how the oil pan is held in place and it seems that the front diff is built into the the oil pan? Am i crazy for thinking this?

Thanks

[floydarogers]

Originally Posted by OTO335i

...
Anyways, I was looking at how the oil pan is held in place and it seems that the front diff is built into the the oil pan? Am i crazy for thinking this?

Not crazy at all. The pan is an aluminum casting, and the diff is mounted to the side of it. There is a hole through it for the right-side half-shaft.

The geometry of this is one of the reasons that the car sits a bit higher than rwd models, and is also the reason that lowering it is not recommended.

[OTO335i]

Originally Posted by floydarogers

Not crazy at all. The pan is an aluminum casting, and the diff is mounted to the side of it. There is a hole through it for the right-side half-shaft.

The geometry of this is one of the reasons that the car sits a bit higher than rwd models, and is also the reason that lowering it is not recommended.

Originally Posted by floydarogers

Not crazy at all. The pan is an aluminum casting, and the diff is mounted to the side of it. There is a hole through it for the right-side half-shaft.

The geometry of this is one of the reasons that the car sits a bit higher than rwd models, and is also the reason that lowering it is not recommended.

Thank you for the insight! So the half shaft does run though it.. I'm assuming that there must be seals there as well, but I don't think the leak is coming from there. I think I would see a big spread of fluid from being spun along with the axle. So to drop the pan I would have to unbolt the diff off the pan and get the half shaft out?

[PhaseP]

Yes there is an o-ring on the differential to oil pan surface sealing, and there is another o-ring between the passenger side axle bearing holding support thing(called "pedestal" on Bentley manual) and oil pan surface there. The tube runs through the oil pan, and the differential fluid splashes and goes back and forth on this tube (not engine oil), providing oil for the bearing on the passenger side support for the axle.
If one of these O-rings were to leak, oil wouldn't splash but you would see the trace of oil on the surface of the oil pan where the differential mates to it (or the "pedestal" on the other side). Again differential oil, not engine.

There are also axle seals as you would expect, one is on the differential at driver side, the other on the "pedestal" on the passenger side. Diff oil can leak from those too, mine did on driver side one time. You would find oil on the outside of the axle inner joints, and also some of the differential where the seal is running down (or the pedestal on the other side if it leaks there)

And yes to get the oil pan out, the differential and axles need to be undone and removed.

The axle going through oil pan in a tube is a result of making front longitudinal engine RWD platform into AWD. Mercedes 4-matic also has one front axle going through a tube inside engine oil pan with differential bolted on the other side of the oil pan, since same engine and RWD layout.

[OTO335i]

Originally Posted by PhaseP

Yes there is an o-ring on the differential to oil pan surface sealing, and there is another o-ring between the passenger side axle bearing holding support thing(called "pedestal" on Bentley manual) and oil pan surface there. The tube runs through the oil pan, and the differential fluid splashes and goes back and forth on this tube (not engine oil), providing oil for the bearing on the passenger side support for the axle.
If one of these O-rings were to leak, oil wouldn't splash but you would see the trace of oil on the surface of the oil pan where the differential mates to it (or the "pedestal" on the other side). Again differential oil, not engine.

There are also axle seals as you would expect, one is on the differential at driver side, the other on the "pedestal" on the passenger side. Diff oil can leak from those too, mine did on driver side one time. You would find oil on the outside of the axle inner joints, and also some of the differential where the seal is running down (or the pedestal on the other side if it leaks there)

And yes to get the oil pan out, the differential and axles need to be undone and removed.

The axle going through oil pan in a tube is a result of making front longitudinal engine RWD platform into AWD. Mercedes 4-matic also has one front axle going through a tube inside engine oil pan with differential bolted on the other side of the oil pan, since same engine and RWD layout.

Now I'm starting to understand the system way more! Thank you for the explanation! I think I'll have to spray the whole area clean and look for the leak again later.

The thing is I have a small oil leak coming from my oil cooler housing that I'm repairing soon, What I'm assuming is that the oil drips down onto the intake tube that runs across the front of the motor and makes it's way towards the back after dripping off the turbo and other parts in that area.