This applies to both Large Drive Units (LDUs) and Small Drive Units (SDUs) in Model S/X. When an internal problem occurs, Tesla does not repair these units — they replace the entire assembly. Handling a failed Model S/X Drive Unit through a Tesla service center can be very expensive.

Coolant leakage in Tesla Drive Units occurs due to wear of the main rotor seal. As this seal ages, it can allow coolant to enter the motor — a known design weakness of the drive unit. The first parts affected are the rotor bearings. Coolant washes out their lubrication, causing a distinct high-pitched whine that becomes louder during acceleration. This is the earliest and most noticeable sign that the drive unit needs service.

If the leak continues, coolant can reach the stator and damage the insulation. This may trigger warnings on the Tesla screen about insulation issues, reduced power, or the risk that the vehicle may not restart. Performance will drop sharply.

Because Tesla coolant is electrically conductive, once enough coolant enters the motor it can create an isolation fault — a short between the high-voltage system and ground. This often triggers additional alerts, and the vehicle may disable itself to prevent further damage. Continuing to drive in this condition can seriously harm the motor or inverter, so towing the vehicle is strongly recommended

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