Model 3/Y: the '990' rear motor, a sturdy workhorse

By bulk owner reports, the 990 rear motor is less prone to inverter problems and is generally more durable than the early 980. When buying a used pre-facelift, many specifically look for the 990.

Know which motor is fitted where from the factory: RWD/SR+ cars came with the 980 (3D1) at the rear, which is normal and not a cause for concern. The 990 is the rear motor of non-Performance AWD cars from roughly mid-2019, plus the Model Y Long Range.

That said, the 990 is not without episodes either: in China Tesla recalled 127,785 Model 3s (built 01.2019–01.2022) over a hardware defect in rear motor inverter semiconductors. The fix there wasn't software: the OTA update only taught the car to detect an impending inverter fault early, while Tesla replaced the defective inverters free of charge under the recall.

How the motor is diagnosed (methods)

Even a reliable motor is worth checking when buying used or at the first symptoms. Typical "symptom → method" pairings (tsk.by breakdown):

• Hum at certain speeds → bearing wear; checked with vibration analysis and a visual inspection for play.
• Body/steering-wheel vibration → rotor imbalance.
• Power drop and rising consumption → inter-turn shorts or winding insulation breakdown; checked with a megohmmeter and winding testers.
• Electronics: error codes, temperature graphs and the fault history are read from the motor controller.

Minsk reference prices, BYN (one shop's figures, not the market): basic motor diagnostics from 150 BYN (1–2 h), extended with partial disassembly from 300 BYN (4–5 h).

Links

• 980 vs 990 discussions: https://teslamotorsclub.com/tmc/threads/980-vs-990-motor-settled.195999/
• Power/efficiency nuances: https://www.reddit.com/r/teslamotors/comments/ioat3d/rear_motor_efficiency_improvements_980_vs_990/
• China recall of 127,785 Model 3s (rear motor inverter): https://cnevpost.com/2022/04/07/tesla-recalls-127785-model-3-vehicles-in-china/