My dad bought a new 59 Impala 4 door. It swayed bad driving down the road. Dad and I both got under the back end trying to figure out why it swayed so bad. We rocked the body side ways, but couldn't see why it moved so easy. 2 years later, I tore up the Turboglide. Dad traded the 59 for a new 61 Impala sport sedan. It drove straight, no sway, a pleasure to drive. So we got under the back end of this one to see if we could figure out the difference. We immediately saw the difference, but didn't know the name of it at the time. The 59 had been missing the panhard bar. No wonder it drove so bad.