I replaced the half shafts in the front not too long ago, definitely within the last 5-10k km, and replaced the seals with oem ones. And there's no leaks from where the half shafts insert into the differential.
I tried removing the fill plug for the differential, and the fluid came right out. I guess it's not a fair test right now, because I have the front of the vehicle raised by 5-10 inches, while the rear is on the ground. But I tried smelling the differential oil, which is also dark / black, and it seems to smell different than the oil from the oil leak.
I may redo the test when I get the vehicle fully level, but I fthink if the differential was leaking, I'd have no fluid there by now. I mean, fron differential only has 0.7l capacity. And the oil is everywhere and leaks on the ground when I park my X5.
I tried cleaning the oil with brake cleaner, maybe ill get another can, but it's hard to get into all nooks and crannies. Once I clean it, I'll maybe drive it for a bit and bring it back put X5 on the lift and start looking for leaks.
But that won't be for a few days, until I get the new oil filter level sensor and refill the engine with oil (and will add some dye).
Maybe ill leave it running while I'm under X5 so I can see where it's coming from...
I just thought it'd be easier to replace everything that can leak, instead of chasing this leak lol. It's gotta be a decent leak for everything to be covered in oil.
I also ordered new gasket for transmission oil pan, who know maybe that's where it leaks, but that fluid would be red/pink, while I got light brown...