My wife drives a '99 V70 that has been rock solid reliable, even with over 170,000 miles. However, since we got the car 4 years ago, the interior has often had a resonance that is annoying. It is definitely engine vibration related. It kind of sounds like you are in a drum when the engine is running. It is most pronounced when at a stop and the car is in drive. Putting the tranny in neutral helps some, but does ot get rid of the problem. At HW speed, the resonance/noise is reduced, but still there and supplimented by the usual road and wind noise. Now that the days are getting cooler, the noise first thing in the morning is getting louder. By the time winter comes, the car will be rattling really loud until the rubber mounts warm up a bit and soften.

I have replaced all the engine mounts: the two main mounts that look like studded botchy balls, the support on the drivers side, the lower torque mount, and the upper torque mount both on the engine and on the firewall. Both the upper and lower torque mounts and the firewall mounts are Volvo dealer parts. I tried the neoprene bushings in the upper mount, and it did not help. There is no unusal vibration coming from the engine. It runs really smooth. so, it is not like the engine is putting unusual vibration into the system. the car is solid with no rust. All the panels are secured and not flapping in the breeze. The 4 rubber bushings between the subframe and the main body frame look fine. Besides, there is so little rubber in those bushings, I can see how they isolate much vibration anyway. (Dealer agreed with this assessment.)

Compared to my '04 XC70, the '99 is very loud and annoying. Even my son's old '94 940 sedan was much quiter.

Any thoughts as to where to look next?
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Gary D