Horrible grinding on decel.
 

So, I have been hearing a faint grinding on decel while in any gear for a while, SOUNDED like it was coming from the front. It was so quiet, and I was told some subies make a similar noise and it's not an issue.

Recently I took out my back seat and rubber wall between trunk and cabin to transport some large stuff. While that area was open, I noticed the grinding/rattling is LOUD, enough to disrupt a conversation. It is definitely coming form below the trunk area (diff, not left or right.)

It DOES NOT happen on accel, it DOES NOT happen on decel in neutral, it happens in every gear when there is no throttle input. The slightest throttle input will make it stop. Hitting the brakes also sometimes makes it stop.

I took absolutely everything out of my trunk, including jack, spare, etc. Still there. Diff fluid level is fine, just below the fill hole. I'm doing to do a drain and fill tomorrow just in case.

I tried making a video with my phone but you really can't hear it over road noise, but it is definitely loud and not normal sounding.

Has this happened to anyone else? Any suggestions?

My car makes the same noise. Hopefully someone can answer this because I would like to know as well.

Glad I'm not alone. Again it's been making this sound for quite some time, I've just now noticed how loud it actually is with the back seat removed. I'll definitely let you know if I find a solution.

Going to head into work tomorrow after stopping by the dealership for diff oil. I'll rack my car up and poke around the diff.

I just did a drain and fill on my diff. Noise is still there, while I was under there I checked the bushings, U Joint, etc. Everything is nice and dry, with no play.

There was plenty of fluid in the diff (almost to bottom of fill plug hole, maybe 2mm under on a level surface) and there were no shavings on the plug, just the normal thin layer of silver goop.

This has got me stumped. Looks like I may be in the market for a new diff if it gets worse.

I have had the same exact problem and so has a buddy of mine, but mine sounds like it comes from right under the shifter, i have not taken anything apart but i was also told it was the gears, but again not sure, if somebodies knows this would be great.

It sounded like it was coming from right under the shifter in my car until I took out the back seat. Now it is very clearly coming from the rear diff area.

Spider gears in the differential could be bad....I've seen that a few times.

bad axle maybe. Does the noise change tone/pitch at all with increased speed? An axle will make a roaring/grinding noise that doesn't change pitch when it's worn out. Like a wheel bearing. It's also load dependent so it would make sense that upon accel/decel.

word to the street

In my case my right axle is bad. But the change of speed does not affect the noise.

@knock, makes it strictly on decel in gear. Sometimes I'll hear a quick chatter during a shift. I am unable to replicate it in any other circumstance, I've tried.

@Paul, what's your rate for diagnosing things like this? I have to go over there sometime soon anyway to grab that A/C compressor, it would be sweet if you could at least sit in and listen to it. I just did a drain and fill and found no shavings, nothing worth mentioning on the magnetic drain plug. Do the gears go bad without actually losing any metal?

I recently had a similar issue but with the sound coming from the transmission area of the car.

I've had the car for about 8 months and it has always sounded this way. I always worried about it but mechanics claimed to not be able to hear it. To be fair it was a pretty subtle sound.

Long story short i was driving with absolutely no fluids in my transmission. Found my tranny dip stick (didn't know we had one of those! sweet!), had a brief cardiac event when i saw it was [B]completely[/B] clean, and then put about 95% of a 1-gallon jug of 75w-90 into it. Noise went away.

Shifts better, sounds better, I don't feel like my transmission is slowly turning into an IED every time i downshift... etc.

There's definitely fluid in my trans and diff. There was a point where my trans was hemorrhaging oil and I always kept a jug of 75-90 in the trunk, I still check it along with engine oil every gas fillup. As for the diff, wasn't low but I just drained and filled it anyway, no change.

I'd check the rear axles just jack the car up and turn the inner cv to see what kind of play it has against the axleshaft. If it's noticeably loose there's the issue. Otherwise I'd look underneath the car for any interference between the axles and exhaust or a bad carrier bearing in the driveshaft.

I'm skeptical of a diff related issue because the noise will get stupid loud and high pitched with a diff bearing/backlash issue and you'd have seen metal in the fluid from any mechanical failure.

I'll check it out tomorrow at work, I can rack my car up, make it easy :-D

Didn't have much time to poke around when I changed diff fluid, hopefully I can find the issue...

Everything looks great. Nothing has excessive play, all the diff mount bushings, cv boots, etc are intact...