Much like most modern transfer cases the ATC300 uses a shift
actuator, or shift motor, to engage the 4 wheel drive system.
The ATC300 is used in the BMW 3 Series and 5 Series from
about 2004 to 2013. There are several variations of the transfer case for those
years, which are 27107599693, 27107599690, 27107613153, 27107613152, but
luckily all of them use the same actuator - part number 27107546671.