chevy tahoe front wheels skidding on tight turns

2001 Chevy tahoe. Front wheels skid, rather than turn, on tight turns. Happens when pulling into and out of parking spaces. Anytime a tight turn is required the front tires just skid. Have had left control arm replaced, front brakes replaced, and front end alignment (2X) and still have the problem. The front alignment improved problem slightly. The outer edges of the front tires are significantly worn (have 7,000 miles on them).