how do i clean out the inside of my impact driver, it's full of sawdust from a deck job and sounds gritty.

Diagnosis

The gritty sound you are hearing in your DeWalt DCF887B is caused by particulate infiltration, specifically fine sawdust and resinous pine particles from your deck job. These particles have been sucked into the tool's internal cavity via the cooling vents during high-RPM operation. Because the DCF887B uses a high-torque brushless motor, the internal centrifugal fan acts like a vacuum, pulling air (and dust) across the motor windings and into the planetary gear set. When sawdust mixes with the factory lithium grease on the hammer mechanism and the planetary gears, it creates an abrasive paste. This paste increases friction, which leads to overheating and a distinct "grinding" or "sandpaper" noise during the impact phase. If left untreated, this debris will wear down the gear teeth and can potentially cause the motor brushes to overheat or the electronic controller to trigger a thermal shutdown. You can confirm this by removing the battery and manually rotating the chuck; if you feel "notches" or a rough sensation rather than a smooth glide, the debris has reached the gear train.

How to Fix It

To thoroughly clean the interior without compromising the factory seals or stripping the gear grease, follow this precise sequence:

1. Power Isolation: Remove the 20V Max battery immediately. Never perform internal cleaning with a live power source, as compressed air can trigger the trigger switch or cause a short if conductive debris is present.
2. External Debridement: Use a vacuum with a narrow crevice tool to remove all loose sawdust from the exterior vents and the gap between the motor housing and the grip.
3. High-Pressure Purge: Using a compressed air nozzle (set to approximately 30-50 PSI), blow air directly into the cooling vents at the rear of the motor. Rotate the tool 360 degrees, pulsing the air into every single vent slot.
4. Trigger Cycle: While applying compressed air to the vents, rapidly pull and release the trigger. This vibrates the internal components and helps dislodge clumps of dust clinging to the brushless motor magnets.
5. Chuck and Collet Cleaning: Open the chuck fully. Use a can of electronics-grade contact cleaner (non-conductive) to spray into the collet area. This breaks down the resinous "glue" that sawdust creates when mixed with grease.
6. Mechanical Flush: Run the tool at the lowest speed setting for 30 seconds, then the highest setting for 30 seconds, without a fastener installed. This allows the centrifugal force to push remaining particles toward the vents where they can be vacuumed out.

If That Didn't Work

• Deep Chemical Flush: If the gritty sound persists, the sawdust has likely bonded with the gear grease. Use a specialized non-conductive electrical contact cleaner. Spray it liberally into the vents and the chuck, then rotate the chuck by hand to distribute the solvent. This thins the contaminated grease, allowing the debris to be blown out more effectively.
• Housing Disassembly: If the tool sounds like it is grinding metal-on-metal, you must remove the outer shell. Use a T10 Torx driver to remove the housing screws. Carefully split the casing, avoiding the trigger wiring. Use a lint-free microfiber cloth and a small amount of isopropyl alcohol to wipe the motor housing. Do not use solvent on the gear grease unless you intend to regrease the tool.
• Gearbox Regreasing: If you open the tool and find the grease is brown or grey (instead of the original translucent white/yellow), the lubricant is contaminated. Carefully scrape out the old "grit-paste" using a plastic putty knife and apply a high-pressure molybdenum disulfide grease specifically rated for impact tools.
• Professional Bearing Inspection: If the grit sound is accompanied by a high-pitched whine, the sawdust may have entered the sealed bearings. In this case, the bearing must be pressed out and replaced, as cleaning a sealed bearing is generally impossible without destroying the race.

Heads Up

• Avoid WD-40: Never use standard WD-40 inside the motor housing; it is a solvent that will strip the essential grease from the impact hammer, leading to premature tool failure.
• Vent Management: When working in high-dust environments like decking, periodically blow out your tools every 2-3 hours of use to prevent "caking" of the debris.
• Battery Port Check: Ensure no sawdust has migrated into the battery terminals. Use a dry cotton swab to clean the gold-plated contacts to prevent voltage drops or overheating.
• Over-Air Pressure: Do not use an industrial air compressor at full 120+ PSI directly against the circuit board, as this can potentially dislodge surface-mount components or push debris deeper into the motor windings.