Mystery Rumbling Sound

1999 Honda Accord XL. Had tune up, rear rotor and pad replacement, rear strut and mount replaced. Still hear rumbling sound [like a bowling ball rolling around] in the rear when I hit a bump; not sure driver or passenger side. Not spare tire nor trunk related. Repair shop doesn’t know what’s causing it. Any ideas?

The good news is that it is not necessarily serious.

I have had a mystery rumbling sound in the back end of my '91 Volvo wagon for 14 years and 200,000 miles. Through those years I have replaced every bushing in the rear end at least once, the shocks, and the rear axle bearings. It has not gotten any worse and it has never caused any problem. The radio hides it. I sure would like to find it though.

If the problem wasn’t there prior to recent repairs, more than likely something went wrong.
If i had it in my shop, i would look at suspension bushings, exhaust/muffler loose, or strut mounts. If i didn’t find anything obvious, i would attach electronic ears and road test vehicle.

Back the car up securely onto ramps, front wheels chocked tranny in park and parking brake on, slide underneath (I like to use corrogated cardboard to lay on), and start shaking things. Odds are that a bushing ia in need of replacement. Common ones at this age are the bushings holding the antisway bar to the chassis. But it could be th exhaust banging, a bushing, or any of a number of other possibilities.

I can’t find it from here, but I’ll bet you can from under the car.