Bushings and other dried out rubber would be my guess. I would a complete suspension check on all 4 corners. Ball joints, tie rod ends, sway bar bushings/brackets, and all the control arms and stuff in the rear end. Its what keeps you on the road!

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Streetside: 1987 Mercedes 300E Petrol Blue/Green
2014 Ford Mustang Grabber Blue
1999 Ford Ranger Green

Dockside: 1968 Eltro 17
1985 Silverton 34C