DeWalt drill making weird grinding noise and stalling - help!

Hey everyone, first time posting here. I've got a DeWalt DCD771 that's been great for years, but recently it's been making a nasty grinding sound when I pull the trigger, and it stalls under any real load. Battery seems to charge fine (it's a 20V max). Anyone have any idea what's going on? I'm not super handy with repairs but willing to try. Thanks!

Grinding noise + stalling = usually the gearbox or the motor brushes. On those DCD771s, the gearbox is plastic and can strip if you've been pushing it hard. Or could be sawdust jammed in the chuck. First thing: take the chuck off and blow it out. If that don't work, open the gearbox and check for missing teeth. I've seen it a hundred times. Also, how old is the drill? Brushes wear out after a few years of heavy use.

Hank's probably right. I had a similar issue with my old Makita and it was the brushes. They're cheap to replace. But before you tear it apart, try a different battery if you have one. Sometimes a weak battery causes stalling under load even if it shows full charge. Also, does the grinding happen only when drilling or also when just spinning? That'll tell you if it's the chuck or the gears.

Thanks guys. The grinding happens even when just spinning, no load. And I tried another battery, same thing. So probably not the battery. I'll try blowing out the chuck first, then maybe open it up. Is there a video you recommend for replacing brushes on a DCD771? I don't wanna mess it up.

YouTube has tons. Just search 'DeWalt DCD771 brush replacement'. It's a 15-minute job if you have a Torx set. While you're in there, check the gearbox grease – if it's black and gritty, clean it out and repack with fresh white lithium grease. That'll quiet it down. If the gears are chewed up, might be cheaper to buy a new drill. Those DCD771s are like $99 on sale. But if you're attached to it, rebuild kits are out there. Good luck!