BMW E34 front end rattle and its causes
What can cause the E34's front end rattle over potholes?
The most common causes are the strut top mount bearing, the lower control arm ball joint, drop links (the anti-roll bar links) and worn reaction rod bushings. Also check for a missing shock absorber bump stop and a loose tie rod or strut top mount nut.
How do I recognise a drop link rattle?
A drop link clinks over sharp bumps, for example on cobblestones. A loose ball joint instead gives a lower thud. Replacing the drop links stopped the rattle in several cars.
What are the E34's lower control arm and reaction rod, and how do they wear?
The transverse arm is the lower control arm and the diagonal one the reaction rod. Both are below the axle and have a ball joint. The reaction rod bushings and ball joints can wear quickly if the parts are cheap. The wear can show up as the wheels knocking and vibrating.
How do I replace the control arm bushings?
It is easiest to press the rubber bushings out at a workshop. At home, the outer ring of the old bushing is sawn through so that it comes off. Polyurethane bushings go in by hand. Tighten the bolts only when the car's weight is on the wheels.