I have a 2010 manual E61 535xi with 166k miles, and every time I brake semi-aggressively with the clutch disengaged I get an uncomfortably loud clunk as if something is shifting while braking and hitting on the chassis. I can feel it in the brake pedal, and in the floor when I sit in the back and someone else is driving. It feels like a bowling ball or something is rolling forward and hitting something in the hatch. If I brake slowly, or if I slow down while in gear I don't notice it. I notice it on acceleration as well, it's not as pronounced or loud, but I can definitely feel something shift when I accelerate.

The entire front end suspension is replaced in the last 5k miles (shocks, all control arms, end links, etc...), but I have no record of rear suspension being replaced. When I look underneath the diff bushings look good, no cracking and diff hangs in the center of the bushings. Transfer case/transmission mount was also replaced in last 20k miles. No engine vibration noticeable, and when I rev the engine it barely moves.

The fact that it happens under braking that I can reliably replicate with the clutch disengaged tells me it's not driveline, so only thing left is subframe bushings? Or am I missing something? I would think if the subframe was shifting that violently it would be easy to move with a pry bar while jacked up, but it seems pretty stiff?

Any help someone has to offer would be great.

 

Have you checked the flex disc?

 

I have looked at the guibo, can't see any cracking or separating. I would also think a flex disc wouldn't cause the loud thud while braking with the clutch disengaged? It reliably makes the loudest thud if the clutch is disengaged and I brake swiftly.

 

I think to actually find the issue you're going to need to put it on a lift. By disengage do you men you have the pedal push in when it makes the noise?

 

Correct, by clutch disengaged I mean the pedal is pushed in.

I had it in the air yesterday, prying around on bushings to see if I could find a smoking gun, but nothing definite. It's hard to tell though when the subframe is hanging on the bushings.

My next plan is to mount a go pro on the outside aimed at the wheel, or underneath aimed at the subframe mounts to see if I can catch the wheel shifting when accelerating or braking.

 

I would of had someone in the car pushing the gas and braking with the clutch in while I was under it.

 

Don't mean to resurrect an old post, however wanted to provide an update.

I was running 19" style 172 staggered wheels which are insanely heavy with a low offset. As a last resort I put my other 18" style 125 wheels back on that are quite a bit lighter and have a higher offset, and all my clunking has gone away since.

It's possible that this is only masking the issue for now, and the heavier lower offset wheels were making one of the rear rubber bushings deform too much, which will eventually get worse and come back even with lighter wheels. But for now I drive in peace.

 

Heavier or lighter wheels aren't going to make any real difference to the suspension in terms of odd noises and looseness - at least not a 100.0% change in behavior. My bet is that the original wheels lug bolts weren't properly tightened, or maybe had the wrong taper profile to securely lock them in place.

IIRC, the E60 lug bolts have a tapered (cone) shape. Whatever, they do have to match the profile of the bolt recesses in your wheels.