2008 Audi A4 2.0T.
Specific condition is when I back into my driveway, I'm driving down the street, turn the wheel to the left and line the car up. Then shift to reverse and cut the wheels right and start backing. Only when I cut the wheels right when reversing after driving forward does it chatter. I feel the chatter in the wheel and it's audible as well.
The condition is intermittent and I cannot produce it on demand.
Steering rack looks healthy (no damage, no leaks, everything feels tight). Power steering fluid has been replaced (mineral oil based per spec). It has lost fluid on occasion but again, no leaks are detectable (I repair as needed when there is a leak and keep the engine top and bottom washed down and clean).
Been over all the suspension components that move and don't see any issues.