w126 front end rumbling

[dtrain]

'89 420 sel with 185k

i have been rebuilding most of the front end in recent months in part because it is 20 years old and to finally get rid of all the squeaks and groans...

below is a list of everything i have replaced to date (i think this is everything...). the problem is that i still have a rumbling noise in the front end at lower speeds when traveling over any bumps ranging from the lip of concrete on my driveway apron to railroad tracks. anytime i am driving over an uneven road, it rumbles constantly. i don't notice it at higher speeds but the highways are in pretty good shape.

any suggestions would be appreciated.

Upper control arm
Steering knuckle (lower ball joint)
Guide rods
Guide rod mounts
Tie rods
Spring shims
Engine mounts
Transmission mount
Eccentric pin kit
Idler arm
Steering damper
Sway bar bushings
Lower control arm bushings
Front and rear Shocks (about 4 years ago)
Engine shocks (about 5 years ago)
Repacked front wheel bearings
New Michelin mxv4 plus tires (front end alignment)
Subframe bushings
Suspension brng brkt