Is breaking front end parts common with a locker installed. I don't really hardcore trail ride but just want to be prepared.
Wade
It mostly depends on your driving style. I wheel with a couple of other guys and we all run 33s (actually one of them just stepped up to 35s) with lockers front and rear. We wheel mainly rocks/rocky trails. None of us have broken anything in the drivetrain. We do all now run the aftermarket chromo front axles, but a couple of us started out with the stock axles with birfield rings and I think the other guy was running stock axles without birfield rings.
Like was said, the main thing is you don't want to back up with the wheels turned.....that is very hard on the birfields and they are easier to break, when they are at an angle (wheels turned).
I also try to keep the wheels as straight ahead as possible, when going forward, and needing to be on the gas.
You also don't want to "hop" the tires. If you are trying to make it somewhere and the tires start hopping/bouncing, stop. When the tires start hopping/bouncing, that puts very high stress loads on the drivetrain and can break stuff.
Bottom line is just to use some common sense when wheeling and you should be fine.