One problem related to rear suspension shock absorber has been reported for the 1999 Buick Lesabre. The most recently reported issues are listed below.
Shocks in rear of vehicle are unstable. This causes the vehicle to bounce up & down, even with people in the front & the back. Would even have luggage in the truck & vehicle would bounce. Would have a controlling problem if not slowing down. Took vehicle to dealer & was informed by mechanic that problem is normal.