Why does my steering get hard when I make a sharp turn and my vehicle jerk

IF you mean vehicle is 'bucking' (almost as if it stops and then goes) while turning sharp on dry pavement (?) .. Suspect problem with AWD transfer case.. In any event... Test drive by savvy personnel and full scan test (includes the AWD system) suggested... Note: Bucking is a sensation related to ANY 4wd that is engaged while *turning hard* on dry pavement like, say in a parking lot... Your AWD system is 'supposed' to automatically compensate for that..