722.6 five-speed automatic: overbuilt but not immune to failure

The 722.6 (5G-Tronic) automatic is widely considered robust and overbuilt, rated for very high torque and shared across many Mercedes models. However, owners report the conductor plate and a fluid-contamination line as the usual trouble spots, at least one out-of-warranty major failure, and confusion over whether the once 'lifetime sealed' unit needs periodic service.