[HedMan]

Originally Posted by smassey321

I have not read about any plastic gear issues on the newer ATC450 that comes with the 8 speeds transmissions.

The ATC450 TCs (which is what is on the 2011-12 X5) have a different actuator than the previous models.

Previously, the actuator looked like this:

The motor (2) uses a worm gear to turn a regular gear (inside 4). That regular gear gets stripped and can be easily replaced (since the whole actuator unit can be removed from the TC).

The ATC450 actuator looks like this (#3):

The actuator (3) is really just the motor. It turns a worm gear that turns a regular gear that is inside the TC itself, so there is no easy, $20 fix (at least as far as I have found).

I can confirm that disconnecting the wires from the actuator will make the shuddering at slow speeds problem go away...but it also disables ABS, DSC, etc., so is not a long-term solution. And without removing and cracking open the TC, I don't know if the shuddering is from a problem with the actuator (which would be an easy replacement), or is from one of the gears (which would require replacing or rebuilding the TC, I think).

The most reasonably priced rebuilt transfer case I've found is https://www.ebay.com/itm/BMW-X5X3-TR...oAAOSwYIxX23r2 ($1,450, but $400 is a refundable core fee) but it looks like it doesn't come with the actuator, so you would need to reuse the old one (or replace it for another $650-ish).

The process for replacing the TC looks straight forward:
1. Remove everything in the way (transmission support, covers, heat shield, exhaust).
2. Remove the drive shafts (from the engine, to the front, to the rear)
3. Unhook the wires to the TC
4. Unbolt the TC and remove it
5. The same in the reverse order

Nothing too complex, but looks like it would be difficult if you don't have a lift and some air tools.