I am also experiencing an oil leak similar to the one you describe. I took the X5 to the following repair shops/dealer with their diagnosis:
1. Baron BMW - Transmission input shaft seal leaking - Also High pressure power steering pump hose leaking -Parts and labor $1500 - $2000.
2.Autobaun Motors (Indie) - Motor mount oil seals (?) leaking - Valve covers leaking - Transmission input shaft not leaking. - Parts and labor $1,300. Also Rear Wisbone replacement needed and Driveshaft "clicking" when engaged in gear, needs to be replaced - Parts and labor $2,400.
3. Autopia (Indie) -Upper oil pan(oil separator?) leaking. Rear suspension squeek caused by worn wishbones. Driveshaft a little noisy but not serious yet (109,000 miles) parts & Labor oil leak -$800.00 Rear suspension $1100.

So, the oil leak has actually slowed down to a minor drip and I am ignoring it for now, mainly because I have been spending on average over $300 a month on repairs for this piece of crap since i bought it (used in 05'). Needless to say, this is my last BMW of any kind. What a disappointment.

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