W108 suspension creak at high wheel speed
 

My 1970 280SEL has a scary suspension creak when hitting bumps at speed. It sounds almost like a rusty hinge, but low pitched. I typically notice it when hitting uneven sections of road on the highway. I can also make the sound happen if I hit a speed bump faster than I should. It seems to be coming from the passenger front, but might be the passenger rear.

The entire front suspension/subframe is a junkyard transplant that looked to be recently rebuilt. The camber adjusters and kingpins seem to be tight, and the squeak is not coming from there. The sound only occurs at high wheel speed (e.g. on bumps). I want to say it's the shocks, but they seem to hold pressure.

I also noticed that the inner lower control arm pivots were a little loose, and would not take grease. I tightened the nuts, but was unable to squeeze any grease in.

Any suggestions on what the culprit might be?

I had very squeeky and creaky suspension. it sounded BAD. Like metal scraping/creaking. New rear lower control arm bushes and full chassis grease got rid of all noises. any dry bushing in rear should be changed.

also check to see above and below the springs in front and rear. make sure the rubber shims are in good order and not touching metal.