Yes, but offroad you won't turn any better if you have a high traction situation. I would suggest you stay away from that type of full time lock, especially in the front. For the rear, I wouldn't also weld it, unless you know what could happen and how to fix it. Most who ask about it don't know the repecussions. About the only time I would consider welding the carrier to lock is if I broke spider gears and wanted to wheel for the weekend/week and would replace it once I get back home or I have spare rears to completely bolt in during a race.
All the Posilok does is eliminate the vacuum shifter to a cable shifter. The axles stay the same.