I agree with checking the fluid. i had a jeep cherokee with a lift on it and bigger tires and it stressed the power steering alot. it whined for a day after i went off roading and stressed it alot. It finally stopped but i could still feel a difference. i did a power steering flush and new fluid with a high tempreture point and it fixed it. that is my bet. i did the flush at my work (a dodge dealership) using a wynns flush kit. somewhat expensive if you dont get a discount.