Transfer case gear ASM with drum clutch (ATC45L)

The clutch drum (or basket) acts as the housing for the internal clutch plates, springs, and spacers. It is critical for the transfer case’s ability to engage and disengage the four-wheel-drive system, ensuring that torque is correctly distributed between the front and rear axles.

Common symptoms include a noticeable ‘jerking’ or ‘shuddering’ sensation during acceleration, clicking noises when turning at low speeds, or the ‘4×4 Malfunction’ light appearing on your dashboard. These often point to worn clutch components within the drum.

This part is designed specifically for vehicles equipped with the ATC45L transfer case. This unit is commonly found in BMW X3 (F25), X4 (F26), X5 (F15), and X6 (F16) models. Always verify your transfer case type before ordering.

If the internal walls of the drum are scored, heat-damaged, or if the gear teeth are worn, replacing the entire assembly is highly recommended. Installing new plates into a damaged drum will lead to premature failure and poor AWD performance.

The most common causes are mismatched tire sizes (different tread depths or brands), which puts constant stress on the clutch, or failing to change the transfer case fluid at recommended intervals, leading to excessive friction and heat.