Shimmy 2000 buick 70k miles

car body shakes side to side between 30-40 mph. steering wheel does not. all tires rotated and balanced. rims are good. tie rod ends and ball joints seem ok. one tie rod end replaced. my mechanic is stumped.

I’d Bet On A Bad Tire. A Belt Could Be Separating In A Tire Or A Rim Is “Out”. Did The Mechanic Check The Tires / Wheels For Radial And Lateral Run-Out ? That Should Be Done With A Problem Of This Nature.