Tesla Drive Unit Repair & Maintenance

Besides the high voltage battery, a Tesla drive unit is the next most costly component to replace. What’s a drive unit? In the case of brands like Tesla, Lucid and others, the drive unit is a compact assembly that contains:

  • The traction motor (or drive motor).
  • The inverter, which controls the motor speed and direction.
  • The final drive assembly, consisting of a reduction gear and a differential.

Every Tesla vehicle has a rear drive unit, and all wheel drive models feature a second drive unit at the front. If anything goes wrong inside them, Tesla will only replace the complete drive unit. This can be pricey, with a Model S/X Large Drive Unit (LDU) replacement currently running around $9000 through a Tesla service centre.

As Alberta’s hybrid and EV service leader, we’re happy to offer less costly repair options – and even upgrades for Tesla drive units. We now stock all of the required bearings, seals and internal parts to provide everything from a small repair to a full overhaul.

Photo gallery – Tesla drive unit repairs at My Garage:

After a technician diagnoses a problem inside the drive unit, we’ll remove it from the vehicle. This involves lowering the front or rear subframe, so we have to perform a wheel alignment afterward. The drive units weigh up to 300 pounds, so a hydraulic table is used to lower and transport them. Now we can open and disassemble the drive unit and make any repairs necessary; everything from replacing noisy bearings to repairing coolant leaks or problems with the inverter.

A common symptom of a failing Tesla drive unit is a hum or whining noise at speed, caused by worn rotor bearings. Unlike the normal electrical whine heard during acceleration, this noise will occur regardless of throttle position and typically gets louder as road speed increases. Worn rotor bearings can be replaced as long as the noise is addressed early enough. Because these bearings spin at up to 22,000 RPM, a specialized ceramic bearing must be used. These bearings are only manufactured by SKF and are difficult to find, with many low quality fakes for sale online. The correct bearings are only manufactured in Italy and must be imported from Europe.

This noisy drive unit was left too long and is not repairable.

Internal rotor seal coolant leak issues – Large Drive Unit:

A common problem with the Large Drive Unit (or “LDU”) used in rear wheel drive Model S/X and Performance Model S/X is an internal coolant leak through the motor rotor seal. This will often cause an isolation fault; a short between the high voltage system and ground. Tesla coolant is electrically conductive, and as coolant leaks into the motor it creates a path between the motor windings and the drive unit case. You may see isolation alerts like BMS_w158 and BMS_w142 on your instrument cluster and your vehicle may become disabled once it detects the fault. Continuing to drive the vehicle can cause damage to the motor and/or inverter, so it’s best to tow your Tesla if this happens.

To check for the presence of coolant inside the drive unit, we remove the rotor speed sensor and use a borescope to examine the inside. In severe cases, the sensor will be wet like this:

Tesla never did figure out how to stop the LDU rotor seals from leaking, so newer versions of this drive unit feature a revised coolant manifold that instead “deletes” coolant flow through the rotor. This does not seem to affect the longevity of the drive unit. This upgrade is also available for older drive units through installation of the QCCharge coolant manifold, which we are proud to carry in stock. If caught early enough, we can clean a coolant-contaminated drive unit, replace any worn bearings and then repair the problem permanently by installing the upgraded manifold. With new axle seals installed and fresh fluids, the drive unit will be ready for years of continued service at around half the cost of a full replacement.

Tesla drive unit coolant leak repair
The QCCharge coolant manifold vs OEM.

Tesla Drive Unit Maintenance

Just like the differentials on an internal combustion vehicle, Tesla drive units contain gears and bearings that need lubrication and they contain around two litres of oil to accomplish this. On the Model 3 and Model Y, this oil also provides direct cooling to the motors. Over time, this deteriorates through shearing – the intense pressure between the parts under torque – and through the intense heat generated by the inverter. We recommend to replace the drive unit fluid and filters every 100,000 kilometres to prolong the life of your drive units.

Tesla fluid maintenance