my auto hubs seem warn and keep popping out with quite large bangs.
i was wondering if i manually lock them will i do any adverse damage to them?
When you go 4X driving you are supposed to manually lock them. They are screwed because they haven't been manually locked.
Indeed, when correctly used and maintained "Auto" hubs are as good as the manual ones. The reason they have a 'rep' is thru misuse (in most cases inadvertently) too much grease, wrong diff oil etc.
The "Auto" selection is for lazy mans one off use such as tooling along a track and coming to one little bog hole or creek so to save you climbing out to 'do the hubs' you throw the tranny into 4H or 4L and go thru, select 2WD on the other side, reverse the vehicle to disengage the hubs and fart off again.
The "Man" selection is if you are doing ANY serious 4WD work then you manually lock the hubs and they stay locked in forward or reverse till you manually climb out and unlock them.
Fanging around backing and filling or rolling in and out of challenges with change of direction of rotation in "Auto" causing the hubs to occasionally disengage and then reengage under significant loads is what rounds the teeth off on the Auto Hubs and the symptoms you describe.
Cliff and Ghost are probably correct in that they are 'fubar'. Manually locking them won't hurt but they will probably still let go.