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.

So just the T1 torsen has spider gears? Hmmm...they ruled out ring/pinion gear by saying that since there's no noise going straight, it shouldn't be that.

Now I feel really uncomfortable about their ability to get this car on the road correctly...

What are the other gears in the T2 called?

Edit: By the way, the car makes the same noise from the same location (rear left) on left and right turns alike.

Well, these are spider gears:
http://www.allfordmustangs.com/forum...r-gear-pic.jpg

I don't think Torsen T1s have spider gears either, to be honest.
This is a T1:
http://i46.tinypic.com/2nhi52r.png

This is a T2:
http://i48.tinypic.com/ta2909.png

The center gear would be a sun gear and the outer gears would be planet gears, as far as I'm concerned. Maybe more specifically, it appears they are helical gears.

I'm not an expert, just a hobbiest, so take this for what it's worth. As someone who just rebuilt a diff and has to do it over again because I did it wrong, I can tell you first hand it can be tricky.

Open diffs use spider gears. I think the T2 uses a planetary gear system.

Edit: Wikipedia says T1 uses crossed axis helical gears, T2 uses parallel gears, and T3 uses planetary gears.

[ame="http://en.wikipedia.org/wiki/Torsen"]Torsen - Wikipedia, the free encyclopedia[/ame]

As far as options, I don't know that you have many. I'd try to get a new diff if you don't trust them rebuilding the current one. If they can get an experience person to rebuild it, I wouldn't worry too much about it.

Subaru BRZ manual states the following with regards to "Oil type and viscosity" on a vehicle with an LSD:

http://www.carsaddiction.com/article...nual/#download
(p. 415)

General consensus is that the LS type Motul 300 is not required. Some discussion on it here:

http://www.ft86club.com/forums/showthread.php?t=19218

As a general rule, you don't "rebuild" a torsen, it's replaced. I'm going to assume that';s what they're going to do.

The more I think about it, the more I think they meant to say they are rebuilding the carrier...by replacing the torsen.

Ahh, makes more sense. Yeah, you should be fine.

If you're interested in knowing, the only tricky part is that you want to measure the backlash on the ring gear before swapping the diff. Then, when you put the new diff in (with the old ring gear), you want to match that backlash. Chances are, the current diff shims will work on the new diff, but you want to make sure. They'll also want to make sure the torque to rotate after reassembly is within spec. That, and you want to keep the bearings with their original races, but that's kind of a given.

Update for anyone else with the issue in the future...

Dealership decided to forgo the "rebuild" and instead replaced the entire carrier. No more noise and not only that, I have immensely more grip during hard cornering. I thought my tires were the reason I was breaking loose every time I took a spirited turn but it looks like the differential was to blame.

The question remains: how does this happen?

Honestly? Don't take it as a personal attack, but I've seen people beat on a car that is "at operating temps" because it idled to that temp. The diff is still dead cold and will have issues because of it.


I had a diff rebuilt years ago and the break in procedure was pretty intense and specific because of the heat treatment of the gears and how they have to wear in.


Or you simply got a defect. As the saying goes, "shit happens."

I would support that theory entirely. My "warm up" is usually idling till the needle gets to the cold line (6 o clock position), and then easy driving for ~7-10 minutes.

Is there anything else I could be doing to make sure my Diff isn't stone cold while hooning?

Sounds like you need a friction modifier additive for the diff. Some diff fluids allows the clutches to slip more than others. A friction modifier will help with the noise..

We don't have clutches, though the friction modifier might cause the torsen to be smoother (spec is GL-5 as all GL-5 oils contain the friction modifier...)

i have same sound . i had drift event and weekend drifts . can you inform us what was worn in you diff ??

I actually never found out the real answer. The dealership insists the differential has spider gears but most of my research shows that open differentials are the ones that have spider gears.

is the sound came while course control ???

do you use down shafting to reduce the speed ??

[ame="http://www.youtube.com/watch?v=r0NsMzdFcZg"]Differential Side Gear Backlash Measurement - YouTube[/ame]

[ame="http://www.youtube.com/watch?v=co1LpI8fy4Y"]TorSen t-2.avi - YouTube[/ame]

I'm sorry, course control?


I hadn't really experienced any changes to noise with respect to gear selection but I really only encountered the noise at low speed 1st and 2nd gear tight turns (in parking lots).

For all I know, the noise was present at higher speeds and gears but I simply did not hear it over the engine.

Cruise Control