The transfer case operation check must be carried out in the following order.
Set the manual transmission (or automatic transmission) shift lever to neutral position – "N".
Place the vehicle on a lift or stands. The wheels should rotate freely.
Apply the parking brake (raise the lever all the way up).
Both front wheels should rotate freely in the same direction.
If both front wheels cannot rotate in the same direction, check the front axle gearbox and transfer case. To check the front axle gearbox:
- disconnect the propeller shaft from the front axle;
- check the front axle gearbox, both front wheels should rotate freely in the same direction;
- if rotation is blocked, the front axle gearbox must be replaced.
To check the RK:
- release the parking brake;
- turn both output shafts of the transfer case in opposite directions;
- if they do not turn, then the transfer case is blocked, replace it.
- if the front wheels turn, then check the transfer case for integrity of the shafts, for which it is necessary to remove the transfer case.
Information obtained from this online resource BMWMAN