Hi Darren,
(I've seen the replies to your related question here -
PDC 4 gear less torque? ...)
From my experience, in gear '4' with the torque setting at its lowest '1', I can
just stop my PDC chuck spinning (in other words I can cause the automatic clutch to stop the motor) if I hold the tightened clutch with a heavily gloved hand (like a leather gardening-type glove), but I doubt I'd be able to stop the chuck at any higher torque setting above '1'.
I admit I haven't tried stopping it it at a higher torque setting - and I wouldn't be in a hurry to try doing so - but hopefully this will give you an idea of how my drill (at least) performs. Maybe others will chip in with other thoughts.
Perhaps you could tell us more about what you are/were doing with yours when your automatic clutch is triggered (drilling? or screw-driving for example?).
Colin P.