there's a high pitched whining noise coming from the drill when i use it at low speed, is the motor going bad?

Diagnosis

The high-pitched whining or "singing" noise you hear when operating the Ryobi ONE+ HP 18V Brushless Drill (PBLDD01B) at low speeds is not a sign of mechanical failure or a dying motor. Instead, it is an acoustic byproduct of the Pulse Width Modulation (PWM) system used by the electronic speed controller to manage the brushless DC motor. In a brushless system, there are no carbon brushes to create friction; instead, an electronic controller switches the current to the motor coils on and off thousands of times per second to regulate speed. This rapid switching creates a high-frequency vibration in the motor's stator and rotor windings. When you pull the trigger slightly (low RPM), the switching frequency falls within the audible range of human hearing, manifesting as a sharp whine. As you increase the trigger pressure and the RPMs rise, the frequency increases and the mechanical noise of the planetary gearset begins to mask the electronic whine, making it seem as though the noise has disappeared. You can confirm this is electronic and not mechanical by noticing that the pitch changes instantly as you vary the trigger pressure, regardless of whether you are drilling into a hard material or running the tool unloaded.

How to Fix It

Because this is a fundamental characteristic of the brushless motor's electronic architecture and not a defect, there is no mechanical repair or part replacement that will eliminate the sound. However, you can optimize the tool's performance to ensure the motor is operating efficiently and the noise remains within normal parameters:

1. Verify Gear Selection: Ensure the speed selector switch on top of the drill is fully clicked into position 1 (Low Speed/High Torque) or position 2 (High Speed/Low Torque). If the switch is halfway between gears, you may hear additional grinding noises that can be mistaken for the electronic whine.
2. Check Battery Seating: Remove the 18V ONE+ battery and inspect the terminals for debris. Reinsert the battery firmly until you hear a distinct click. Poor contact can occasionally cause erratic PWM switching, which may alter the pitch of the whine.
3. Test Under Load: Apply a moderate load (e.g., drilling into a 2x4). You will notice that as the motor works harder to maintain torque at low speeds, the whine may shift in frequency or become quieter as the mechanical load dampens the vibrations.
4. Trigger Calibration: Gently cycle the trigger from zero to full power three times. This ensures the variable speed trigger is engaging the controller smoothly without "stuttering" the electronic signal.

If That Didn't Work

If the noise is accompanied by other symptoms, it may be a genuine mechanical issue. Try these alternatives:

• Inspect for Bearing Failure: If the whine is accompanied by a rattling sound or if the chuck has significant side-to-side play (wobble), the front spindle bearing may be worn. This is a mechanical failure rather than an electronic one. You would need to disassemble the gear housing to inspect the bearings for pitting or lubrication loss.
• Check for Gearbox Contamination: If the noise sounds more like a "grind" than a "whine," a small piece of metal debris or a wood chip may have entered the planetary gearset. In this case, opening the casing and applying a high-quality lithium-based grease to the gears can resolve the issue.
• Test with a Different Battery: Use a high-capacity 4.0Ah or 6.0Ah battery. Low-voltage or degraded batteries can cause the electronic controller to struggle with current delivery, which can sometimes amplify the audible frequency of the PWM switching.
• Verify Chuck Tightness: Ensure the keyless chuck is not over-tightened or jammed. A seized chuck can put undue stress on the motor at low speeds, causing the electronic controller to "hunt" for the correct RPM, which increases the audible whining noise.

Heads Up

• Avoid "feathering" the trigger excessively for long periods under heavy load; while the brushless motor is efficient, constant low-speed high-torque operation can generate heat in the controller that isn't always dissipated by the internal fan.
• Keep the motor vents clear of sawdust and debris. The PBLDD01B relies on airflow to keep the electronic controller cool; overheating can lead to a change in the motor's acoustic profile or trigger a thermal shutdown.
• Do not attempt to lubricate the brushless motor itself with oil or WD-40. The motor is a sealed unit; lubricants should only be applied to the gear assembly if the tool is disassembled for repair.
• Remember that brushless tools are generally louder in the "high-frequency" spectrum than brushed tools, but they offer significantly longer lifespans and better battery efficiency.