i dropped my impact driver and now it just makes a grinding noise and doesn't drive.

Diagnosis

The grinding noise combined with a total loss of torque indicates a catastrophic failure of the planetary gear set or the hammer-and-anvil mechanism. When the PBIW01B hits a hard surface during a drop, the sudden deceleration creates an immense shear force on the hardened steel teeth of the planetary gears. If a single tooth shears off or a gear becomes misaligned on its shaft, the motor will spin the input shaft, but the energy will not transfer to the chuck, resulting in a loud, metallic grinding sound. You can confirm this by pulling the trigger slightly; if the motor spins up to full speed with almost zero resistance (no "load" feel) while making a rattling or grinding noise, the connection between the motor and the output shaft has been severed. If the tool vibrates violently but doesn't rotate, the anvil has likely jumped its track or the hammer spring has snapped, jamming the internal mechanism.

How to Fix It

Because the planetary gearset in the Ryobi ONE+ HP Brushless series is pressed-fit and sealed, individual gear replacement is not feasible. You must replace the complete gearcase assembly (Part #RY221012).

1. Remove the 18V ONE+ battery and remove all screws from the outer plastic housing using a T15 Torx driver. Carefully split the clamshell housing, noting the position of the forward/reverse slider and the variable speed trigger assembly.
2. Disconnect the wiring harness connecting the brushless controller board to the motor leads. Be careful not to pinch the wires when opening the case.
3. Unscrew the motor mounting bolts. Gently slide the brushless motor out of the damaged gearcase. Note the exact orientation of the motor spindle to ensure it seats correctly in the new assembly.
4. Remove the old gearcase assembly from the handle frame.
5. Slide the new RY221012 gearcase assembly into the frame. Ensure the output chuck is centered and the alignment pins are seated.
6. Insert the brushless motor into the new gearcase. You should feel a positive "click" or seat as the drive gear engages the planetary input.
7. Reinstall the motor mounting bolts and tighten them firmly to prevent vibration-induced loosening.
8. Reassemble the plastic housing, ensuring the trigger switch is properly seated in its notch before tightening the final T15 screws.

If That Didn't Work

• Inspect the Motor Rotor: If the grinding persists with a new gearcase, the impact may have bent the motor's output spindle. Check for "run-out" by spinning the motor shaft by hand; if it wobbles more than 0.5mm, the motor itself must be replaced.
• Check the Brushless Controller: A hard drop can crack the solder joints on the PCB (Printed Circuit Board). Inspect the board for hairline cracks or loose wires. If the motor "stutters" rather than grinds, the controller is likely failing to sequence the phases.
• Verify the Chuck Collet: Ensure the grinding isn't actually coming from the 1/4" hex collet. If the internal spring for the quick-release chuck is crushed, the bit may be slipping inside the socket, mimicking a gear failure.
• Test with a Different Battery: In rare cases, a drop can damage the battery terminals, causing a voltage drop that makes the brushless motor "cog" or chatter, which can sound like mechanical grinding.

Heads Up

• Avoid Over-Tightening: When reassembling the housing, do not over-torque the T15 screws. The plastic bosses on the PBIW01B are prone to stripping, which will compromise the tool's structural integrity.
• Lubrication Warning: Do not attempt to inject generic WD-40 or automotive grease into the gearcase. The HP Brushless line uses a specific high-viscosity molybdenum grease; adding thinner oils will cause the gears to slip and overheat.
• Impact Protection: If you frequently work in environments where tools are dropped, consider a rubberized sleeve or a dedicated tool holster to protect the gearcase from direct concrete impacts.