I have a small oil leak near the differential, no oil drops on the floor so nothing to worry about, but I can't figure out where it comes from, and why, since there shouldn't be any oil there. The leak seems from the coupling between the propshaft U-joint and the differential input flange, because it leaves a trace all around it.
Here some pics


The pinion seal is dry.
Any explanation for this??

 

If the vertical face of the seal is dry all the way round, there are only two explanations, either the oil is seeping past the outside of the seal or the oil is blowing back from the engine or gearbox. It looks as if there is a lot of oil on the subframe above the diff so the latter looks likely.

Richard

 

Thanks for the reply. There was a slight leak from the transmission before I did a complete service in June. Never found drops on the floor but the sump was wet, and also the rear rubber mount. Maybe it's still dirty from this old leak. There's no smell of differential oil, in fact. I think the only way is clean all the oily dirt and see what happens.

 

I agree. I suspect that it will be old gearbox oil.

Richard

 

I found a picture of the oil pan before replacing the gasket, there is a bit of oil all around, and the air flow under the car may have pushed the oil back to the differential: