Oldsmobile Suspension Questions

I have a '92 olds 98 that bounces shakes going 60-75 ...

I have a '92 olds 98 that bounces shakes going 60-75 mph. I have replaced brakes,struts,tires, and had balancing and an alignment done.

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Have knocking noise in the rear when brakes applied after car has been driven and brake applied at end of the stop. new struts have been replaced. Rear wheel cylinders replace and brake shoes were replace due to a leak and noise never did go away,