It's probaly cheaper to buy a new drill than repair the one you've got. I just bought a new one they have come down in price a hell of a lot .Although I had a Black and decker previously to the new Makita and I wished I 'd have bought a new model Black and Decker rather than the Makita . Small like your Makita model 1/2 the price  powerful , with a Lithium Ion battery every bit as good as Makita and as their sister more expensive brand De-Walt. Not the answer to the question you asked but hey!have a nice day