Front constant joint needs repaired& the bk driver wheel is spinning taking off

I have noticed when I have the steering hard round ( locked ) the car acts as if it doesn't want to move like kangaroo petrol same in reverse! I have also noticed when just pulling away with a slight turn on the wheel ,one off the back wheels spins on its own like there is no grip traction on the one wheel!! The car drives well no noice or pulling banging anything? I am lost I have just bought the car and am getting worried. Audi tt 225,, 140000 miles on the clock the mot is just 4 month old please can you suggest looking at anything. Willie Cormack