Gnob: The locker/welded 3rd member is a dumb animal. It only knows to spin forward or backwards. It has nothing to do with steering. You are correct tires do change speed when going around a curve (I.e. the inside tire slows and the outside speeds up) and with a locker these tires are "locked" at the same speed. Trouble steering increase as your vehicles' speed increases because your inside tire is forceably having to slip when you corner. Which is why if you've ever driven a vehicle with a locked rear end it "yelps" when you corner. Same concept but having the front makes it way harder to steer as speeds increase. However, it doesn't not effect the ability to turn when not in motion on loose gravel, which I have.

My problem is constant moving or not when in 4wd w/ hubs locked. This is why I'm leaning towards a birf or hub issue. Also, if that were the issue I wouldn't be able to turn right either and anyone running lockers wouldn't be able to go any direction other than forward when engaged.