Ive got a makita 18v combi drill....
about 80% of the time when switched to high speed (in drill,drive or hammer
action mod) the chuck spins but there is ZERO torque (you can literally
stop it with your hand). Fiddle with the speed switch for a while and it
works ok again...

Any idea what could be wrong and if I could fix it myself ?
I thought perhaps it was something to do with brushes but i dont see
brushes listed as a spare part for my particular model.