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Subaru intermittent rumbling, vibrating noise

For several months now, my 2002 outback has been randomly generating a deep rumbling noise and accompanying vibration. The best I can describe it is similar to crossing ripple strips, but if they were shallow. If I maintain speed, It will slowly increase in frequency for a minute, then decrease and disappear entirely. If I decelerate, the rumbling also decreases, as if I’m hitting fewer and fewer bumps. If I come to a stop, it disappears entirely, and doesn’t reoccur when I accelerate afterwards.

When it occurs, it seems as if the entire car is vibrating/shaking. I can definitely feel it through the steering wheel, and sometimes a slight squeak will occur from the front passenger side (due to the randomness of the event, it’s difficult to ascertain whether or not there is always a squeak).

By random, the symptom would appear generally once a month. The longest span without it occurring has been at least three months. This has happened at speeds of 50, 60, 65, and 70 mph. I’ve been told by friends that it might be a wheel bearing, and a mechanic has said that my heat shield was loose (and there was nothing they could do or needed to do about it). But as random as it is, I’m uncertain what the cause is.

I would suspect a bearing too.

When it does happen, I would try making few wiggles to left/right to check if rumbling would increase/descrease simultaneously to the slight curves: it would put additional pressure on the front bearings of the outer side, so if it is indeed bearing, you would know if this is left or right one

the fact that it is connected to speed, pretty much tells is is indeed in drivetrain.

other things to check would be oil level in front/back differentials and if you observe any metal shavings in oil.

There are some very good mechanical people here so it might take time to get started in the right direction. In the meantime have you tried to find a dedicated Subaru forum?

There are good cars, bad cars, and then … Subarus
I bet they still have 4 wheels :slight_smile:

talking seriously, yes, you will find a number of Subaru dedicated forums, where people know more about common issues