The symptom pattern

The driver runs perfectly, but bits no longer lock in with the positive click they had when the tool was new. They rock visibly under load, slip partway out, or in the worst case drop free mid-fastener. It creeps up gradually on heavily used drivers, which is why it’s often blamed on cheap bits long after the chuck has become the real problem.

What’s actually happening

A quarter-inch hex quick-release chuck holds the bit with a spring-loaded ball that sits in the groove of the bit shank; pulling the collar retracts the ball to release. Every insertion drags grit through the mechanism, and an impact driver adds thousands of hammer blows per minute on top. Eventually the ball, its spring, or the groove it rides in wears to the point where the grip goes mushy.

There are two impostors worth eliminating first. Worn bits — shanks with rounded retention grooves — slip in a perfectly healthy chuck, and bulk-pack bits get there quickly. And a chuck packed with compacted dust behaves exactly like a worn one, because the ball can’t seat fully.

Working through it

Start with a fresh quality bit and the tug test: insert it without touching the collar, then pull. A healthy chuck holds until the collar is pulled; a bit that slides straight out condemns the retention mechanism. Sticky or gritty collar action points at contamination, so clean the bore — compressed air, a solvent-dampened swab around the ball, and a single drop of light oil worked in by cycling the collar. A meaningful share of “worn” chucks come back to life at this step.

If retention is still weak after cleaning, the wear is real. On the DCF887 the chuck components are serviceable: the parts diagram identifies the nose assembly, and replacement is a bench job rather than a workshop one.

Verdict

Rule out bits, then rule out dirt — both are free. A genuinely worn chuck is a cheap, worthwhile repair on a driver of this quality. The one false economy is ignoring it: a bit that drops out under torque eventually does so into your workpiece, or your hand.