C300

Not sure if this is in the correct location. But, looking to buy car and had them put it on a lift. The last 2 cars i checked, in neutral if one rear wheel was turned the other turned the opposite. the front wheels, one or both turned. this one doesn't CLUNK when spinning one tire another direction, (feel the gears/diff. backlash). the car I just looked at is really nice, low miles. the front wheels do not turn when the rears are. Are the clutches worn, or is this normal. locker not working? This is an 03' RS6. it feels "lighter" than the other RS6 cars i have driven. The Audi dealer says it's in top shape, and want top dollor, but there is no warranty. if it's broke, could be a really bad deal. $$$$ !! Need to figure this out ASAP, Thanks, C300