Clunk Noise When Hitting Bumps

What year is your car?

It could be anything in the suspension. In my case, a "popping" sound started, but it reached a fine point after a few months. At that time, it didn't seem to get worse. Just make a sound over the smallest change in road grade.

Then a few years later, the noise got worse- it turned into a severe vibration/metal on metal squeel. Turned out to be a bad ball joint in the front LCA. I am guessing there was some play in the joint and it bounced around until it burned up/locked up.

Check the struts and strut mounts, too.

Is it coming from the rear? If you're sure it's not the brakes ... Depending on mileage, rear sway bar bushings or shot shocks. Grab the sway bar and pull it up and down. If it moves a little relative to the mounts, replace the bushings. To check out the shocks, pull the bottom off the mount and push pull on it. Should be pretty tough to move in/out but smooth. If it feels stuck or is really easy they're done.

stpete said:

Depending on mileage, rear sway bar bushings or shot shocks. Grab the sway bar and pull it up and down. If it moves a little relative to the mounts, replace the bushings. To check out the shocks, pull the bottom off the mount and push pull on it. Should be pretty tough to move in/out but smooth. If it feels stuck or is really easy they're done.

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I forgot about this- very good point. I replaced my rear sway bar bushings after two years because of this. The rubber shrinks up and instead of tightly holding the sway bar, the bar will bounce around the inside of the sway bar control arms when driving over grade changes.

I also experienced noisy braking due to the ceramic material used in the stock brakes. Switched to aftermarket pads and the noise went way. Made a groaning sound when braking in warm weather- thought a bushing had worn out somewhere. Noisiest new-car suspension I have ever heard.

If all else fails, look into the differential bushing. This is the bushing on top of the differential that absorbs movement from the upper control arm. It's not an easy replacement but do-able with patience. I was surprised how beat up the inner sleeve was after only ~15k miles.
Pics of the inner sleeve. I drilled/dremel-tooled it out, just cut away the rubber. New BMR bushing slides in in 2 pieces, 1/2 from each side.