Common issues & diagnosis
The transfer cases in BMWs do have some common problems.
One of these common problems is the external actuator failing—which is fixed easily & cheaply with a new actuator (which we don’t supply.)
Slightly less common—but more problematic—are internal problems such as worn chains, worn clutch, leaking seals or faulty internal sensors. Sometimes in these situations it makes sense recondition the case—and there are repair kits available for these purposes—but in other cases it’s more cost-effective to replace the entire assembly.
To avoid internal issues with transfer cases you should be regularly changing the transfer case oil (typically every 60,000.)
It is worth noting that in some xDrive models—namely the F25 X3 and F26 X4—uneven tyre wear can produce a thudding in the drivetrain which is commonly misdiagnosed as a transfer case issue.
What is the part's function?
The transfer cases used in BMW’s RWD-based AWDs differ in design from the ones used in their FWD-based AWDs.
RWD-based AWD drivetrains
The RWD-based AWD drivetrains have a north-south engine direction. The transfer cases are attached to the end of the transmission, distributing power to both a tail shaft and front prop shaft—which connect to the rear and front differentials respectively.
The role of the transfer case in this drivetrain is to intercept the tail shaft and distribute power to the front wheels.
FWD-based AWD drivetrains
The FWD-based AWD drivetrains have an east-west engine direction—with the engine (sitting right-hand side) bolted to the transmission (on the left.) The transmission has two flanges, one for the LHF output shaft, and the other for an intermediate shaft that passes across the engine to the RHF output shaft. The transfer case sits around this intermediate shaft, where it hooks into it with notches, using it’s rotation to drive a pinion that outputs power to the tailshaft.
The role of the the transfer case in this drivetrain is to intercept the front wheel axis, and transfer power from it to the rear wheel axis.
How to determine fitment compatibility
There are usually multiple, non-exchangeable types of transfer case within any given model generation.
To determine fitment compatibility of a transfer case for your vehicle, we recommend matching the BMW part numbers from the catalogue.
Provide our team with your vehicle’s 17-digit VIN, and we’ll check our stock for compatible match.
Interchangeability between models
There is some interchangeability of transfer cases between sister models, as well as between models sharing a common platform.
