[ajsalida]

Originally Posted by *********

Holding the DTC button for more than 3 seconds to turn both off allows all four wheels to spin in snow....I've done it..

Good to know, that is what I thought. That means the e-LSD things still works AND the transfer case is operating as intended.

Have you ever jacked up your car on all 4 wheels? The front wheels can spin freely while the back is locked up. I think because the front can spin freely, it is disengaged from the rest of the drivetrain. When the car is on, the wet clutch pack in the xDrive system engages the front diff. and the axles can only go in a 40:60 split with rear bias..

OK this in not exactly right. Clutch pack in the transfer case will vary between a min of 50% rear to a max of 100% rear in most conditions people will see. You are right about 40/60 on dry roads going straight with no wheelspin. When car is OFF clutches to front axle are disengaged as you say. RWD is always engaged as the driveshaft coming out of the tranny is a solid link (no clutches between it and the tranny or rear diff) so the minimum TQ to the rear is always 50%.

Also when you reach highway speeds, no power is going to the front so I would assume the xDrive system disengages the front axle so less parts are moving and the front wheels are just rotating because the rear wheels are pushing the car.

I think up to 100 MPH on dry road driving straight not turning it is still 40/60. I have also read at very low speeds (parking lots) FWD is disabled when rear has traction (no wheel spin). Above 100 MPH it disengages front. I have read elsewhere that speed is a bit lower but cannot confirm.

Also there is a very confusing case described where on glaze ice, when the rears both have zero traction and the fronts have some, BMW says xDrive sends almost all TQ to the front, which is impossible unless you write science fiction for a living. Or write politcal speeches.