Car:
1993 FD. R1. Delrin bushings. Koni yellow shocks. Tein S-tech springs. LS1 swap, HSC tie rod ends. Stock front suspension otherwise (arms, sways). Rear trailing arms and toe rods are RE units. Rear pillowballs replaced about 1,500mi ago. Rubber shock upper mounts have about 10,000mi. Redline shockproof differential fluid. Polyurethane steering rack to subframe bushings.

Problems:
1. Frontend vibration. Speed and heat (assumed) related. Problems present above about 40mph. Problems worsen as drive time increases. Vibration isn't enough to cause a handling problem, but is enough to be an annoyance. Vibration happens regardless of pavement surface. Seems to be cyclical in nature (oddly enough). Vibration seems to be transmitted in such a manner that the steering wheel vibrates circumferentially.
2. Popping noises from front suspension. Happens when stopped while turning steering wheel. Not always noticeable. Attempted fix #1 was for this problem.
3. Knocking noise around front passenger side suspension. Happens during hard left turns. Attempted fix #1 was for this problem as well.
4. Differential whine. High pitched whine, changes in relation to speed of vehicle. Becomes very annoying above 60mph. Causes skipping of CD player at ~67mph.
5. Clunking in rear. Pillowballs were replaced and almost remedied problem. Problem thought to be related to excessive backlash of differential pinion, noted to be about 5*. Not sure how this relates to normal.

Attempted fixes:
1. Removed, cleaned, and regreased front upper A-arm after noticing looseness. Suspect bolts were not torqued properly. Retorqued and threadlocked arm to chassis mounting bolts. No binding or looseness in upper A-arm ball joint was noted.
2. Lubricated front sway bar to chassis mounts to solve a creaking problem.

Notes:
1. Checked HSC tie rod ends for play. None noticed.
2. Knocking sound (similar to problem #3) appears to be present when harsh force is applied to rubber upper piece on front PS shock towards centerline of vehicle. Happens once or twice, then stops. Cause not yet found.
3. Differential whine suggested to be related to worn pinion to housing bearing. Not checked.
4. Steering system has a slight bit of play to it, thought to be related to power steering quill shaft.

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Anyways, does anybody have any insight as to what could be causing the problems noted?

Thanks in advance.

 

Seems like you've been pretty thorough, but have you checked the swaybar mounts for cracks? Sometimes they're not as apparent as you'd think. My passenger side mount had cracked but it was near the top of the mount, near where it bolted to the chassis, and hard to see. Made noise similar to what your describing.

 

1. Front tires/wheels out of round and/or out of balance.
a. Natural vibration frequency changes as tire pressures increase.
b. slightly different tire revs/mile side-side will cause vibration (shimmy) to come and go as vibration inputs from the 2 tires match or cancel

 

I don't believe that lubricating the front bushings is a procedure actually called for in the FSM. I also don't believe it actually does anything.

I believe your problem is with the balljoints - probably lower ball joints on the lower control arm.

I have what sounds like similar noises and I'm 90% certain its my ball joints. Going to replace them (and the lower control arms overall) very soon.

 

Gracer7: It's not, but these aren't stock bushings either. They were binding up a bit, and now they're not.

DaveW: The tires are quite likely out of round, they were badly flatspotted not too long ago and are coming back into round.

Sgtblue: Forgot to mention that I have widefoot swaybar mounts. I'll inspect them for damage anyway.

 

wheel bearing?