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.

It is important to know which motor is fitted where from the factory: RWD/SR+ cars came with the 980 (3D1) at the rear — that is normal, 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. Firmware doesn't fix hardware — it only diagnoses it.

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/