4x4 making loud bangs, but two wheel drive is ok. should I fix or sell? on 1999 Mercury Mountaineer

my 4x4 isn't working well, when I steer sharp it makes loud banging noises. the brake pedal shakes and steering wheel does too when braking making me think the rotors are bad. the vehicle is squirrely on the road and going down the road feels like I'm running on flat tires. Is there hope or is it time to move on? what kind of repairs am I looking at? I put a new transmission in it in 2010 so I am not sure why the 4x4 wont work.

Asked by for the 1999 Mercury Mountaineer