the chuck on my 887 impact wobbles side to side a little, makes the bits not sit straight.

Diagnosis

The wobble you are experiencing in your DeWalt DCF887B is caused by a failure of the output anvil or the front-end bearing assembly. Because this tool uses a 1/4" hex collet rather than a traditional rotating chuck, any side-to-side play indicates that the internal tolerances of the anvil have been compromised. This typically happens due to "side-loading," where the tool is used to pry or twist a fastener at an angle, forcing the anvil to shift off-center within the housing. Over time, the hardened steel of the anvil wears down the race of the front bearing, or the anvil itself becomes slightly bent. You can confirm this by inserting a high-quality, straight impact bit and holding the tool perpendicular to a flat surface; if the bit tilts more than 1-2 degrees or you can physically wiggle the bit while the tool is powered off, the internal seating of the anvil is shot. This creates a "run-out" effect that makes it nearly impossible to drive screws flush without the head slipping.

How to Fix It

Replacing the anvil on the DCF887 requires a complete teardown of the hammer mechanism. You will need a set of Torx drivers (T10 and T15) and a small bench vise.

1. Remove the battery and any bits from the collet. Unscrew the outer housing screws located on the sides and bottom of the tool.
2. Carefully split the plastic clamshell housing, taking care not to pinch the trigger wires or the LED light circuitry.
3. Slide the motor and gearbox assembly out of the housing. Locate the front nose piece where the anvil is seated.
4. Remove the retaining ring or snap ring that holds the anvil in place. If the anvil is seized, you may need to use a punch and a light hammer to tap it out from the rear of the gearbox.
5. Clean the bearing seat with a lint-free cloth and a small amount of solvent to remove old, contaminated grease.
6. Press the new replacement anvil (Part # compatible with DCF887 series) into the bearing. Ensure it seats fully and flush against the internal hammer stop.
7. Apply a small amount of high-temp lithium grease to the anvil shaft before sliding it into the collet.
8. Reassemble the housing, ensuring the trigger assembly is seated correctly before tightening the outer screws.

If That Didn't Work

• Replace the Front Bearing: If the anvil is new but the wobble persists, the front bearing race is likely pitted or ovaled. You must press out the old bearing and install a new high-load miniature ball bearing to restore the center axis.
• Check for Collet Spring Failure: Inspect the internal spring-loaded ball bearings inside the hex drive. If the spring is weakened or a ball is chipped, the bit will not be centered, creating the illusion of anvil wobble. Replace the collet assembly entirely.
• Inspect the Gearbox Housing: Check for hairline cracks in the magnesium or alloy gearbox casting. If the housing itself is cracked, the anvil will shift regardless of how many times you replace the part. In this case, the entire gear head assembly must be replaced.
• Verify Bit Quality: Test with a brand new, precision-ground impact bit. Low-quality, worn-out bits often have "mushroomed" ends that don't seat deeply in the anvil, causing a deceptive wobble.

Heads Up

• Never use the impact driver as a pry bar; side-loading is the primary cause of anvil failure and will void your warranty.
• Avoid using "universal" adapters that add length to the bit; these increase the leverage acting on the anvil and accelerate wear.
• Periodically blow out the nose of the tool with compressed air to remove metal shavings and construction dust that can jam the collet mechanism.
• If you feel the tool vibrating excessively in the handle while driving, stop immediately; this usually indicates the internal hammer is misaligned, which will quickly destroy a new anvil.