I have an E39 that recently developed a squeak that seems related to the suspension of the vehicle. Squeak happens when driving on road with small to large bumps & when pushing down on the right rear bumper. I have removed rear wheel and sprayed anyhing that looked like a likely culprit (all rubber bushings body mounting points and springs/ shocks. WD-40 did not help, nor did oil. I did get some temporary relief from spray silicone but that lasted less than a week. And of course when I applied the silicone I sprayed all of the points mentioned above. Anyone ever diagnose this problem and/or can provide a more permanent solution???