power steering bad vibration

[jpliddy]

hi all
well over the last few weeks when driving my car has serious vibration when steering wheel is turned even coming out of a junction then sometimes just pulling on to the drive when steering wheel is turned slightly . do you think the problem is ATF wants changing or is it something worse i got the front end of the ground today with engine running i turned steering wheel full lock both ways and the problem was there while the engine was running i gave one of the wheels bit of a kick and it stopped .but started again on test drive it seems to do it if i go over uneven surface too . no oil leaks .
any help please