1995 960 Rear Noise

150 km/hr and than disappears. It is kind of like differential or bearing grinding noise. What could be the reason. Maybe not enough fluid in the differential, or bearings. Anybody else had this problem?

The car is automatic.

Thanks Adam

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Start with getting the differential lube topped up ASAP. If it has leaked out and is running dry the differential will soon seize. Replacing the lube will probably save the differential although there may still be noise.

Mike

150 km/hr and than disappears. It is kind of like differential or bearing grinding noise. What could be the reason. Maybe not enough fluid in the differential, or bearings. Anybody else had this problem?

The car is automatic.

Thanks Adam

It's Probably (but only probably) not a wheel bearing. The sound from those will likely be noticeable at lower speeds as well. Possibly a differential going out. Unfortunately, with differentials, when it gets to the point where you hear the noise, it's too late to just top off the fluid; you're running on borrowed time. I'm not familiar with the limited-slip setups the Volvo's sometimes use. If your car is equipped with one of these, something in there might be causing the noise.

But there are a few other possible causes for the noise. Driveshaft U-joints or the carrier bearing are possible candidates. If the driveshaft itself has been dinged, it might be slightly out of balance, which could also give the symptoms you're describing. A tire going bad might even do it. Those last two would probably be accompanied by some noticeable vibrations, however. I've even seen a loose trim piece vibrating in the wind mimic a grinding mechanical component at high speeds. Also, grab your tailpipe (make sure it's cool, or wear thick gloves) and shake it vigorously to see if there's anything loose and rattling in the exhaust system.

Sorry to make things more complicated instead of easier. It's all wildcard guesses without being able to hear the noise. A good idea might be to find a trusty mechanic and take him for a ride.

Cheers, Walt