I'd check the suspension for worn, loose components: tie rod ends, ball joints... Does it steer straight, no pulling? Does it only pop when the steering wheel is turning?Does the r/p have the boots on each end? Is there no noise when it's driving in a straight line? When was the last time you greased the wheel bearings? Does it happen under full throttle turns or normal turns? You're gonna need to lift her up and have a close look.