Cheers Weasel. Dont think i'm under warranty, car has done 79k. Still think thats a bit early for a major component! Looks like i'm going to have to go wag my finger.......

Usually it is a result of tire size differences (front vs rear) taking its toll on the clutches. That is usually the case when someone buys new tires for one axle and leaves the mostly gone tires on the other.

But hopefully when you tell the BMW dealer that couldn't find the cause before what you found, and that unplugging the t-case motor stopped it, they will have no problem helping you out. And subsequently you will be teaching them about a very uncommon problem. Good luck!

Damn, good job Weasel56. I just love this message board. So much good advice, especially for folks like me that are newbies to BMW's.