Loud rear suspension bang when wheel drops

[goltho]

Every time the car "takes off" i.e. the weight comes off the rear axle e.g. an inclining undulation or ramp ends and the rear wheels drop suddenly, there's a long bang from the rear passenger-side corner. I've rebuilt the front suspension on two 75s but part from changing a pair of rear springs, have little experience of the rear end.

There's no indication of play in any direction with the wheel jacked up but then it's fully unweighted so that I can't emulate the movement. Any thoughts?

Dougie.