M5 Guru (>2000 posts)
Join Date: Nov 2008
Location: New England
Thanked 762 Times in 621 Posts
Another thought about checking the differential. After the 'spin check', maybe check the differential seals? I mean, is there fluid in the case? Is there signs of leaking fluid? No or low fluid would be a sure way to smoke one. Just a thought.
We're all just throwing ideas around and I don't want to overwhelm you but I'd be checking the transmission aft before I got too heavy into the engine.
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim
8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim