On the corners of convertibles there are what's called "cocktail shakers" or vibration dampeners which were originally installed on every first gen convertible Camaro to help prevent vibrations. They were installed due to a very flexible body in the convertible models because of the lack of the roof structure. Some reinforcement was added to the convertible rockers and floors but it wasn't enough to prevent all vibration problems. The cocktail shakers are large cans with a suspended mass on a spring in a viscous fluid that are mounted on the corners - 4 in all. They were tuned to a resonant frequency of the convertible that caused the vibration problems. When the body was subjected to loading that would otherwise tend to make it oscillate, much of the energy was instead absorbed by the motion of the masses in the cocktail shakers - which reduced the vibration in the convertible body. If the cocktail shakers have been removed, order the coupe ML001 Mono-Leaf rear springs. Mono Leaf springs use the 802 series rear shocks. Multi Leaf springs use the 703 series rear shocks. All lowered cars with either spring use VKB222 shocks.