I had a similar problem with an '02 AWD Chevy Venture Van. It started making a howling/grinding noise when making sharp turns just after the warranty expired! They quoted me a fix of $5500. One service manager told me of a TSB put out by GM about changing the versi-track fluid with a new type they had developed. $50 per quart! He said to change the fluid, take it to a parking lot and crank the wheel as hard as I could and drive it around in a circle for 5 min. I did and within 1 min. the noise stopped. Never had any more trouble with it after that. Lots of other problems with that POS, but at least I didn't have to spend 5K on it. I got on line and read a lot of people with the Chevy Venture and Olds Bravada having this problem. They had a class action suit against GM over it in Canada. Should have been a recall.