Additional Noise

My morning commute is about 33 miles. After about 30 miles, when I almost reach my destination, my 1992 Buick Century makes an additional noise besides the normal engine, muffler and road noise. It sounds like a BRRRRRRR…, but only when the car is moving, not idling. I thought it could be a temperature- related transmission issue. I noticed it was low on transmission fluid, so I added some. It still makes that noise, but only after I traveled about 30 miles. I didn’t notice it last year when my commute was only 16 miles. Does anyone have any ideas what could cause it?

Sounds like your car’s getting cold…needs a new thermostat.


Is this a metalic sound…air passing over something loose…???

You may have a loose heat shield near the exhaust that is vibrating from the moving air turbulence.

Does the sound seem to keep pace with the engine speed, or the cares speed.


Good ideas above. Another idea, sometimes a catalytic converter going south could result in an unusual exhaust sound as it heats up. Mechanics can do a back pressure test at a pre-cat test port. Normal values are 2-4 psi.

A muffler heating up and changing configuration is another possibility I suppose. If it has to be one of these, hope it is the muffler.

Is there anything different about those last few miles, even something as minor as a slight grade or different road surface? Or a slightly different speed? It would help if we knew where the noise seemed to come from. It can be hard to tell, but every little bit of info helps.

You bring up a good point @MarkM, I’ve had times where my truck sounded totally different just because of the road surface. Even the sound bouncing off buildings will make a vehivcle sound completely different, but I doubt for 10 miles.


Agreed, but he is only talking about the last two or three miles of his commute. That it was only the last bit is why I was wondering about road surfaces, as many commutes stay on freeways until near the destination, at which point they may turn off onto secondary roads. The same on the way home. I can’t imagine what on the car would take 30 miles to develop. Cars heat up quickly.

I don’t think there is a change in the road surface. Now, it seems like the car is doing it sooner during my commute. The noise appears to come from the back end of the car. It sounds like a geary, metallic sound.

Bad differential, heating up?

Sounds like you may just have to wait a few days and it will fail catastrophically … not something you want to happen.

“Bad differential, heating up?”

These Buick models are FWD, so if the noise is actually coming from the rear–as the OP states–then I think that we can rule-out a failing differential. The only thing that I can think of in the rear of the vehicle that could make this type of noise is the fuel pump, but somehow I don’t think that the fuel pump is the source of the noise. Of course, I could be wrong…

Could it be a wheel bearing heating up?

Could it be a wheel bearing heating up?

Yes, jack up each rear wheel and spin it.