I need some help in diagnosing a ride quality issue on stock my 2012 Cruze 2LT. For the first 6000 miles the ride was smooth and quiet, then like the turn of a switch, the ride got choppy and jiggly. I can feel it in the seat and the steering wheel at most speeds. It seems like some drive component has grounded out on the chassis or a heavy drive component is shaking. Tires were rotated at 4000 and 8000 miles and always at 32 psi. Underbody pan was cut out for the fire recall at 4000 miles. Dealer cannot find anything.
Does anyone have an idea of what I should look for?