remove the battery

lye it flat with the screws pointing up at you use a screw driver and undo them all

lift the case off ( the trigger part might also lift)

remove all the plastic outer parts

so you have the drill motor gearbox a switch gear in front of you

take the drill chuck in your hand or a vice and look inside you will see a reverse thread screw

undo the screw turn to the RIGHT

un screw the chuck

unscrew the next plate this will be holding back a spring get rid of this too

you will see or hear a load of ball bearing falling everywhere (un less you catch them) i would recommend removing all these

replace the reverse thread screw

clip the motor wires

DONE

to make it work as needed you need some (i think) 2.5mm diamter grub screws to replace the ball bearings screw them down until you can't turn the shaft but hand (not overly tight though)

think ive covered it all

enjoy

alex