my dewalt 20v drill just clicks when i pull the trigger, battery is charged and it feels like it's trying but nothing spins

Diagnosis

The clicking sound you hear when pulling the trigger on your DeWalt DCD771C2 is the sound of the motor's armature spinning and the trigger switch engaging, but the torque is not being transferred to the chuck. This indicates a mechanical failure within the planetary gear system. Specifically, the teeth on the sun gear or one of the planetary gears have stripped or sheared off, causing the gears to "slip" or jump rather than mesh and rotate. This typically happens when the tool is used under heavy load without the clutch being set correctly, or if the drill was forced in reverse while under high torque. You can confirm this by checking the gear selector switch on top of the tool. If the drill clicks in both Speed 1 (low) and Speed 2 (high), the failure is likely in the final drive stage of the transmission. If it only clicks in one speed, the issue is isolated to the specific gear set for that speed. Because the motor is "trying" (indicated by the humming or clicking), the electrical circuit, battery, and trigger assembly are functioning correctly; the break is entirely mechanical.

How to Fix It

To resolve this, you must replace the transmission assembly. On the DCD771C2, the gears are housed in a modular assembly that can be swapped without replacing the entire tool.

1. Remove the 20V Max battery pack and set it aside to ensure no accidental trigger pulls occur during disassembly.
2. Using a T15 Torx driver, remove the long housing screws located on the side and top of the gear casing. Be careful not to lose the smaller screws that secure the clutch ring.
3. Carefully pull the motor and trigger housing away from the front gear housing. You may need to gently tap the casing with a rubber mallet to break the seal of the plastic mating surfaces.
4. Slide the motor armature out of the rear of the gear assembly. Note the orientation of the motor pinion gear.
5. Remove the stripped transmission module. This is the internal gear cluster that connects the motor to the chuck spindle.
6. Install a new replacement transmission assembly (ensure the part matches the DCD771 series specifications). Align the planetary gears carefully so they seat fully into the housing.
7. Slide the motor armature back into the new transmission, ensuring the pinion gear meshes perfectly with the first stage of the planetary set.
8. Reassemble the housing, tightening the T15 screws in a cross-pattern to ensure an even seal and prevent the casing from warping.

If That Didn't Work

• Check the Chuck Spindle: If the gears are intact but the drill still clicks, the internal threads of the chuck may have stripped from the spindle. Try removing the chuck entirely and pulling the trigger; if the spindle rotates but the chuck doesn't, you need a replacement chuck rather than a gear assembly.
• Inspect the Gear Selector: The sliding speed switch on top may be stuck in a "halfway" position between Speed 1 and Speed 2. Use a can of compressed air to blow out any construction debris from the selector switch and toggle it firmly back and forth several times to ensure it is fully engaged in one position.
• Verify Motor Pinion Wear: Examine the small gear (pinion) on the end of the motor shaft. If the teeth on the motor itself are rounded off, a new transmission won't help because the motor cannot drive the gears. In this case, the entire motor assembly must be replaced.
• Check for Obstructions: Inspect the vents and the area around the motor for metal shavings or debris that may be jamming the planetary gears, preventing them from rotating despite the motor's effort.

Heads Up

• Grease the Gears: When installing a new transmission, apply a small amount of high-pressure lithium grease to the planetary gears. Running these dry will lead to rapid wear and another failure.
• Clutch Management: To prevent this from happening again, always adjust the torque clutch ring (the numbered dial) to the lowest setting necessary for your task. Forcing the drill through a material that exceeds the clutch limit puts immense stress on the planetary gears.
• Avoid "Shock" Loading: Avoid switching the drill from forward to reverse while the motor is still spinning at high RPMs, as this creates a mechanical shock that can shear gear teeth instantly.
• Battery Heat: If you are using the drill for heavy-duty boring, allow the motor to cool. Overheating can soften the plastic components within the gear housing, leading to misalignment.