When I'm turning my 55 on a slope the steering jerks after a full turn of the steering wheel. anydeas what would be the cause of this?

Ideally, put a jack under each lower control arm as close to the wheels as possible. You don't have to jack it off the ground, just take some weight off. See if you can feel anything odd as you turn the steering wheel, then get someone to do it while you watch the steering arms.

 

It could be play in a steering joint that is slopping from one exteme to the other as the wheel goes past a certain point, or play inside the steering box..