Diff whine with clutch engaged + axle seepage
 

My car has 35,800 miles and for the last ~1000 miles I've been hearing this differential whine sound when making low speed tight turns such as U turns or K turns. Or even maneuvering around a parking lot. I believe it sounds exactly like typical diff noise on these cars which is very faint but this is easily audible. I would consider it even loud because it can be heard over a conversation with the radio off.

The last time I changed the diff oil was at 32,000 miles and I used Motul Gear 300 as it meets the specifications per the owner manual and is supposed to be better than stock fill. Anyways, my first assumption was I did not fill the diff fluid properly. Today I had the chance to finally have the car in the air after not driving for two weeks because of worries. I checked the diff fluid, properly full, fluid looks good and smells as terrible as always. So I sealed the differential fill plug back up with a new crush gasket.

So the fluid isn't the issue. Makes sense because when making a tight turn in gear, I get the noise. As soon as I put it in neutral and keep the speed and turning radius constant, the noise is instantly gone.

Is it a bearing?

Also, while the car was in the air I got the opportunity to find that the boot on the driver's side axle closest to the differential is seeping grease. No tears in the boot but I think it's just not tight enough perhaps. I have no reason to believe these are related issues.

As of right now I have an appointment next week for Subaru to "look at it". I have a feeling I'm going to be told "that's how the differential is supposed to sound" which is a flat out lie and RE the axle, they'll probably just tighten up the clamp and ignore any missing grease.

Does the axle need to be replaced in this situation? It's lost a reasonable amount of grease just from what I can tell looking at where grease has landed on the underbody.

Any help is appreciated.

If relevant - my only modifications around this area are RCE springs, SPC LCA's, "aftermarket" diff fluid, Perrin shifter bushing and MTEC shifter springs.

Not familiar with the RCE spring or how much drop they give but you may find some info of value here: http://www.ft86club.com/forums/showthread.php?t=49511
Be interested as to what they say about the dif when you bring it in.
Sorry not a lot

Change the fluid in the rear diff, if it's making noise while making a sharp turn then the clutch packs are slipping in the limited slip causing chatter / noise.
Did you use Motul 300 or the Motul 300 LS? You need to use the LS version.


they will prob change out the boot in question on your CV axle.

There are no clutch packs on our diffs.

So you don't have a limited slip?

Pretty sure Ozzman is right on this one. Why would a Torsen need the LS version? I'd like to hear an explanation for this. I want to politely say you're mistaken on both accounts.

I don't see a reason to change the diff fluid yet. It has less than 4,000 miles on it. I can't honestly expect to belief something like synthetic differential fluid could break down with such little driving. I've spent 15K miles on a previous fill of Motul Gear 300 with no issues.

The differential in this car is a Torsen T2 (mechanical), not a clutch diff.

Maybe it has something to do with the way the torsen diff distributes loads to the wheels during fluctuating wheel speeds. I seriously doubt its an axle issue since you only get the noise on turns.

Do you get the same noise on left and right turns?

The repair manual states to use the specific LX oil , check the BRZ manual section AD-26. there has to be a reason for using the Additive version of the rear differential fluid.

I apologize about the clutch pack statement, I had a brain fart and was thinking of 06 my X-runner that has the mechanical limited slip, Wrong forum..

CV joint noise is typically a clicking noise that happens with frequency of the wheel rotation, the noise is usually more apparent when the joint is flexed, so in the 86, this would mostly be under rapid accel to compress the rear end, and deflect the CV joint further.

Bearing noise is typically a growl or grumble, sometimes it's more audible when a load is applied one way or another. I've heard some bearings sound like a howl as they're dying.

Gear noise sounds like a mechanical whine most apparent when load is applied in one direction or another. The whine may change frequencies with whatever element is causing the noise, if it's the diff, the frequency will change with vehicle speed.

Spec for the diff is GL5 while Motul Gear 300 is GL4/GL5...


Motul Gear 300 LS is GL5 and probably better suited (don't as me why a torsen needs the friction modifier I'm simply looking at specs).


Outside of that, you probably have other issues.


On the axle issue, it should be replaced and I've never seen them seep grease, there has to be a tear somewhere IMHO.

What exactly would make a GL4/GL5 worse than a specific GL5 only fluid for this application? I truly don't know.

I am willing to bet anything that all they will do is replace the boot and clamps for the axle. I know the axle should be replaced in reality...

Edit: Tomorrow I'm taking the car into Subaru for them to "check it out". Guessing I won't be driving my car for awhile.

Update!

The spider gears in the diff are ruined based on a diagnosis by Subaru today. No root cause found. They're ordering parts for a rebuild that will take place next week.


And typical stuff with the axle, replacing the boot and repacking the joint :bonk:

Interesting, I have heard of the diff grenading before but its rare. Considering how many of these cars get tracked/boosted/drifted/hooned the number of gnarfed diffs is pretty small. I wonder if it's a freak tolerance thing.

What exactly are they calling spider gears here? Because there aren't any in our diffs.

Here is an exploded Torsen T2 diff:
http://wiki.r31skylineclub.com/image.../DiffFAQ_4.jpg
http://images.thesamba.com/vw/gallery/pix/483695.jpg

No spider gears there.

I doubt it's the ring/pinion gear.

Not saying it isn't the actual diff making noise, I just think they aren't using the right terms, which makes me leery that they can even rebuild one correctly.