Annette H

Hi,

My 1996 Subaru Impreza Outback has been making these low (deep), loud, droning, rumbling noises for a while now, always at low (<55 mph) speeds, and often when applying little or no gas. The car will make this noise with or without braking, but the sounds are intermittant, not constant, but they last a while (10-15 seconds at least during which time I usually try changing gears or doing something with gas pedal, usually with no effect at all) each time they occur. The sounds are not related to steering as far as I can tell, and they don't sound like a wheel bearing problem (I've had those before), but the whole car seems to vibrate with the harmonic. Also, the sounds tend to run in streaks -- like it will make the noise on and off for fifteen minutes then seem to disappear. Does anyone have any idea what this could be?

Brit_in_Japan

Try knocking it into neutral when it is making the noise/vibration. Does it make any difference? From what you say it doesn't appear to matter what gear you are in, if so that would eliminate engine and gearbox. It would point to something downstream from the gearbox (driveshafts, propshaft, diffs, wheel bearings/wheels/tyres).

If it was making that severe a vibration, I doubt it would be wheel bearings as they would already be knackered beyond use.

Out of balance wheels/tyres cuase vibration, but unlikely to cause the noise you are refering to. It may sound stupid, but check all the wheel bolts/nuts are tightened up properly. If loose they can cause vibration and noise, especially when at constant speed with little/no throttle. Check that first, you don't want a wheel falling off !

Annette H

Yes, thanks, I have tried shifting into neutral without getting any immediate effect. The noise is so bad I've done most everything I can think of to try and get it to shut up. The problem is, nothing really works immediately. If I shift into neutral, I also let up on the gas and eventually the RPMs dip under the level where the noise occurs and the noise stops. If I step on the gas (after putting the car back in gear), the noise starts up again when we hit the RPM range where they seem to be a problem. Eventually, when we hit highway speeds, the RPMs increase beyond the point where they are a problem. I am not really sure where the cut-off points are, but I'd say the car is more likely to do its low, loud drone when cold, and more likely be noisy around 5-35 mph at 1800-2300 RPMs. So that doesn't quite rule out the engine. Also, if I get off a highway and slow down into the problematic range, I rarely have that low rumble-roar-drone thing going on. Seems like the noise is coming from the rear end somewhere about two feet or more behind the driver's seat and in the middle of the car, although the sound is so loud it makes conversation somewhat difficult. I mean, you don't have to scream to be heard over the drone but you have to talk loudly.

One thing you have given me is the inspiration to be more scientific. The next time the confounded noise occurs, I will stop the car and see what happens if the drive train is not engaged (neutral) while I slowly vary the RPMs. If I can't get the car to make it's horrible noise when it
s stopped, that should clear the engine of blame. (I don't think it is the engine or the bearings/wheels or tires, since I think I can rule most of those out.) I suspect the drivetrain. How can I differentiate between the drivetrain, propshaft and diffs?

I have about 135,000 miles on the car, but I need to nurse it along for a while and I don't trust the mechanics I've been going to for seven years because they just tried to charge me $400.00 more than the Subaru service guys for a clutch assembly replacement. That was a real shocker, and I'm still kind of hurt. On the other hand, the Subaru service guys charge too much and their hours stink.

I really appreciate the help, by the way. Thanks very much!

Brit_in_Japan

[QUOTE=Annette H]How can I differentiate between the drivetrain, propshaft and diffs?QUOTE]

Good question. Listening to where the noise comes will give you a pointer. Sounds like it comes from behind the front seats, so rules out front driveshafts and front diff I would think. So that leaves centre diff, rear diff etc.

Beyond that, I wish I knew. Soon the UK will wake up and others with more experience can help you out.

Are you based in the US or Oz ? Owners in those countries may be able to recommend a garage you can trust.

Good luck.

Annette H

Thanks very much! I'm in Phoenix, Arizona (US) on the far north side near 16th St. and Bell Road. There's a Subaru service center within easy biking distance but if there is any trustworthy independent mechanic nearby I'd be glad to know of it.

I'm heading off to sleep now (almost 1AM here now). Your day must be drawing to a close, what is it almost 5PM?

Anyway, I am glad I joined up and asked... I don't feel so alone anymore!

Have a great evening!