No idea if that's the clutch or not (I'd guess its the part which selects low or high range as the 12v single speed drills don't have that on them I don't think) but if you have not yet took your other drill apart yet you might want to leave it together for now. The LH Thread screws that hold the chucks on can be really tight and leaving the drill assembled in its case gives you a lot more to hold on to when you are trying to get it undone.