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Old 08-20-2013, 08:17 PM   #1
gathermewool
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Default Rear Diff Oil Dark Gray After ~1,200 Miles!

Car: 2008 Subaru WRX STI
ODO: 62,226 miles
Miles on oil: ~1,200 (allegedly - the dealer said they drained and refill it to see what the oil looked like, and that it was amber-colored, but that may not be the truth. Note: the rear diff only recently started overflowing from the vent port, which leads me to believe that either they did drain and refill it, albeit with too much refilled, or my worsening binding issue is some how to blame.)

I posted recently about my rear differential being over-filled by the dealer while they were trouble shooting a binding issue I'm having that I was hoping Subaru would cover 1,000 miles outside of the warranty. See more HERE:
So, the dealer only removed the fill plug and drained until no more came out. They would not admit to how much came out, but that's besides the point. I asked whether the diff being over-filled would cause the oil to aerate or foam up. They replied that it was not likely. Well, ~1,200 miles after they say they swapped out my rear diff oil with bulk oil, here's what it looks like:



Here's the before and after of the drain plug:




Here's what the oil looks like after ~1,200 miles:











//


Compare all of that to the factory fill @ 17,000 miles:






Thoughts? If you have any questions outside of the bobistheoil guy link I posted in the beginning, please feel free to ask.
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Old 08-20-2013, 08:35 PM   #2
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i have drained a good few rearends with the factory fill on subarus and MOST of them have looked like that

and its almost impossible to over fill the rearend....in fact...id LOVE to see how it could possibly be accomplished

and i think you would be worried about the grass being too green and the sky too blue

i think you have more serious issues.......
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Old 08-21-2013, 12:08 AM   #3
gathermewool
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I agree that I have more serious issues, though it's not impossible to over-fill ..

1. Stick tygon in fill port
2. Pump and pump and pump
3. Pull tyon out, see that oil is streaming out of fill port
4. Quickly put temp sensor back into fill port
5. Over-filled.

Case in point, the tubing that came with the pump I used wasn't an interference fit, but oil still streamed out after I removed it from the port. Now, I had a quart bottle that I was pumping from, so I knew that soon into the second quart bottle I should expect to see it overflow (which I did not until after I removed the tubing to verify,) but had I been pumping from another container of unknown or large volume, then I'd have no way to track where I was until I eventually pulled the tube and saw oil flowing out.

Also, oil was over-flowing through the vent port on top of the diff and running down the diff cover. Even short drives would evidence overflowing. When I cracked the temp sensor after only 5 mile drive from work to the shop, oil flowed out. I tightened the sensor back up, immediately seating the o-ring, so that the dealer could also see that itw as over-filled.

//

I was told way back when that the color of my factory-fill oil was normal, some even saying that it was a special break-in lube that contained high moly content, though the UOA doesn't validate that claim (a scant 1ppm Mo.) Should that still be true for subsequent changes?

With all of that being said, my concern/question are:

1. Does gear oil usually foam, as shown in the very first pic?

2. What is the color indicative of? Excessive iron wear from the gear teeth; bearing wear?

3. If it is indicative of something, what? Detrimentally improper preload; improper pinion placement?

I'm working with the dealer to try and have something done under warranty, but that may be a losing battle.

Last edited by gathermewool; 08-21-2013 at 12:15 AM.
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Old 08-21-2013, 12:33 AM   #4
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Also, the binding has not changed at all after the fluid change. I used M1 75W-90 LS. I used a friction-modified lube just in case Subaru accidentally installed an '06 plate-type LSD at the factory.
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Old 08-21-2013, 07:42 AM   #5
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dealer said the problem is your center diff (from your other thread). You might get a 2nd opinion.

Another simple diagnostic is to disable your center diff controller. When done the default of the center diff is open. That will eliminate - or not - the control of the center as a problem. I do no know how to do that, on mine I have an aftermarket dccd controller and it's easy.

FYI your center diff and 6mt share the same fluid. That being said has the fluid been changed in the 6mt, ever? Try subaru extra S available in qts from fred bean parts. My dealer didn't have a clue about putting subaru extra S in my 6mt and did that myself.
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Old 08-21-2013, 09:23 AM   #6
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After reading a bit, it seems that some aeration of the gear oil is completely normal.

Quote:
Originally Posted by mhoerath View Post
dealer said the problem is your center diff (from your other thread). You might get a 2nd opinion.

Another simple diagnostic is to disable your center diff controller. When done the default of the center diff is open. That will eliminate - or not - the control of the center as a problem. I do no know how to do that, on mine I have an aftermarket dccd controller and it's easy.

FYI your center diff and 6mt share the same fluid. That being said has the fluid been changed in the 6mt, ever? Try subaru extra S available in qts from fred bean parts. My dealer didn't have a clue about putting subaru extra S in my 6mt and did that myself.
I appreciate the reply.

The dealer only changed their diagnosis after they told me they would only cover half of the repair cost for the rear diff, at which point I asked about a million questions, pointed out obvious flaws in their logic (e.g., I don't have a plate-type LSD nor a viscous-coupling), and concluded that their diagnosis wasn't conclusive enough for me to hand them a grand to do the work (this was before I saw the black oil, mind you.)

A couple of days later they explained that they now think it's the clutch pack in the center diff catching due to misalignment and grabbing due to the shift in the clutch vs mating surface after 60k miles - kind of like how grooves form between your brake pads and rotors, is how it was explained. This I didn't buy either.

I do plan on getting a second opinion, but there aren't any shops nearby that I trust, and I haven't had time to make a trip to one I do. It's on the list, though.

While driving in a tight circle in a parking lot I can feel the increased resistance as I shift the DCCD from full open to fully locked. It's a smooth resistance (that feels nothing like the binding I'm experiencing in the rear diff) and it goes away immediately when I open the diff back up or shift to AUTO. I would like to rule out the center diff electrically malfunctioning by disabling it, but I'm not sure how to disable the DCCD.

The tranny was changed out at around the same time as the rear diff at ~17k miles, using Motul Gear 300. I swapped that out earlier this year with Redline NS. Both the factory fill and Motul came out looking slightly darker than new, though I didn't send out a sample for analysis. No change has been noted in shift quality.
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Old 08-21-2013, 04:49 PM   #7
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Another datapoint. After ~50 miles of driving this afternoon the highest reading rear diff temp was 131F. There was a long period near the end where I was traveling steadily through 45 MPH and then 25 MPH zones before reaching home, so the diff had plenty of time to cooldown from earlier, more-aggressive driving.
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Old 08-21-2013, 10:44 PM   #8
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Quote:
Originally Posted by gathermewool View Post
Another datapoint. After ~50 miles of driving this afternoon the highest reading rear diff temp was 131F. There was a long period near the end where I was traveling steadily through 45 MPH and then 25 MPH zones before reaching home, so the diff had plenty of time to cooldown from earlier, more-aggressive driving.
i dont think 131*F is too high...and i dont know at what temp the diff warning light comes on....but that sounds like it isnt too hot

Quote:
While driving in a tight circle in a parking lot I can feel the increased resistance as I shift the DCCD from full open to fully locked. It's a smooth resistance (that feels nothing like the binding I'm experiencing in the rear diff) and it goes away immediately when I open the diff back up or shift to AUTO. I would like to rule out the center diff electrically malfunctioning by disabling it, but I'm not sure how to disable the DCCD.
this sounds like normal dccd operation.....iirc if you pull up the handbrake enough to illuminate the light on the ins panel, that opens the center diff

and my research tells me that the 08 sti uses a type 2 torsen rear diff that does NOT want or need any 'LSD' gear oil or additive....a 75w90 gl-5 is what is suggested i think
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Old 08-22-2013, 06:56 AM   #9
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If you somehow got water in your rear end, it will cause the gear oil to foam up.

The water in the oil, can turn to steam, and cause metal to metal wear of the gears.

Send in some of the fluid and have it analyzed-it might not even be gear oil?

Sounds like your DCCD is working. I'm not sure how the center diffs clutch pack can shift? I call bs on that one. I have a pic of one opened up on another thread.
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Old 08-22-2013, 08:13 AM   #10
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Quote:
Originally Posted by gathermewool View Post
While driving in a tight circle in a parking lot I can feel the increased resistance as I shift the DCCD from full open to fully locked. It's a smooth resistance (that feels nothing like the binding I'm experiencing in the rear diff) and it goes away immediately when I open the diff back up or shift to AUTO.
As mentioned all above seems like your center diff is controlled and operating normally.

Quote:
Originally Posted by gathermewool View Post
I would like to rule out the center diff electrically malfunctioning by disabling it, but I'm not sure how to disable the DCCD.
Uncle scotty is correct, pulling the ebrake will open the dccd. Actuation is by the ebrake switch and not mechanically, so pull the handbrake just a bit and your center diff should open.

Quote:
Originally Posted by gathermewool View Post
While driving in a tight circle in a parking lot I can feel the increased resistance as I shift the DCCD from full open to fully locked. It's a smooth resistance (that feels nothing like the binding I'm experiencing in the rear diff)
how do you know the rear diff is binding? Not trying to be a pita, just trying to isolate the problem. I know that newly freshened plated rear diffs do some pop and crackle. But your's isn't plated. Check your rear wheel bearings. I had severe wear on a front that resulted in very nasty binding at low speeds (had a good reason to let it go that long!).

Last edited by mhoerath; 08-22-2013 at 08:25 AM.
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Old 08-22-2013, 09:06 AM   #11
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Quote:
Originally Posted by Uncle Scotty View Post
i dont think 131*F is too high...and i dont know at what temp the diff warning light comes on....but that sounds like it isnt too hot



this sounds like normal dccd operation.....iirc if you pull up the handbrake enough to illuminate the light on the ins panel, that opens the center diff

and my research tells me that the 08 sti uses a type 2 torsen rear diff that does NOT want or need any 'LSD' gear oil or additive....a 75w90 gl-5 is what is suggested i think
It doesn't sound very high to me either, considering I remember reading some time ago that the temp warning light energizes at something like 250-300F.

You're right, and the Motul Gear 300 that I used previously was a GL-5 lube not specifically for clutch-type LSD's (unknown FM add pack, but LS not specifically listed.) I chose M1 LS this time to sort of cover my bases. As small a chance as there might be, I wanted to rule it out. And while the FM adds may take up some room in the ase lube otherwise occupied by EP adds, the risk of slightly more wear occuring in a diff that will most likely be replaced soon doesn't matter much.

Quote:
Originally Posted by point78 View Post
If you somehow got water in your rear end, it will cause the gear oil to foam up.

The water in the oil, can turn to steam, and cause metal to metal wear of the gears.

Send in some of the fluid and have it analyzed-it might not even be gear oil?

Sounds like your DCCD is working. I'm not sure how the center diffs clutch pack can shift? I call bs on that one. I have a pic of one opened up on another thread.
I don't believe there was ever a time where my diff was submerged to the top of the pumpkin where it might enter the vent port, let alone in the past 1200 miles.

The fluid has the sulfuric smell to it, though that could very well be the previous fill. However, I don't think Motul has a lot of Sulfur in its add pack - I believe due to its dual GL-4/5 rating. I have the sample in the bottle shown in the pics. I'm just waiting for my Dyson analysis kit to come in the mail.

If I can I'll try to get a sound clip of the issue asap.
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Old 08-22-2013, 09:42 AM   #12
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Quote:
Originally Posted by mhoerath View Post
As mentioned all above seems like your center diff is controlled and operating normally.



Uncle scotty is correct, pulling the ebrake will open the dccd. Actuation is by the ebrake switch and not mechanically, so pull the handbrake just a bit and your center diff should open.



how do you know the rear diff is binding? Not trying to be a pita, just trying to isolate the problem. I know that newly freshened plated rear diffs do some pop and crackle. But your's isn't plated. Check your rear wheel bearings. I had severe wear on a front that resulted in very nasty binding at low speeds (had a good reason to let it go that long!).
I'll pull the e-brake until the light is in on the dash and observe the effect.

I'm going to botch the description up, but here goes:

Conditions:

1. It's most prevalent and 100% repeatable while backing uphill and turning the wheel. The wheel does NOT have to be fully or even close to fully locked for this to occur. It will start to bind with the steering wheel going off-center and become worse the further the wheel is turned.

2. It has been getting worse, and can now be felt during any low-speed turning at more than idle power level.

3. While moving and turning, the binding sound/feel worsens if gas is given, and is worst of all when turning from a stop.

4. Seems to get worse as the oil heats up, after some driving. I.e., the binding may be substantially worse after coming off the highway and trying to turn left quickly into a neighborhood between pockets of traffic.

5. It may still be binding, but higher speeds while turning, say, through some twisty roads don't produce any audible sound nor any vibrations that I can tell.

Symptoms:

Parking in my condo complex I usually pull straight into the lot and then back sharply into one of the spots (it's kind of tight, so a sharp turn is required. I'd also experience the binding if I were pulling forward into the spot as well, fwiw.) As I begin to move in reverse, there's a vibrating feel/sound like ghghghghghghgh, that turns into more of a loping guhguhguhguh as the wheel is turned further and more gas given. As soon as I straighten the wheel or clutch in everything goes back to normal.

I've removed the cover and listened with my head just above the spare, as well as followed the car with my head near the rear and that is where I'm nearly positive the noise is coming from.

Last edited by gathermewool; 08-22-2013 at 09:50 AM.
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Old 08-22-2013, 11:19 AM   #13
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I believe gear oil's anti wear structure is sulfur/phosphorus.
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Old 08-22-2013, 02:44 PM   #14
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If the noise/vibration goes away when the clutch goes in, prob not a wheel bearing.

If I back up with my center diff locked, feels like something is breaking, lots of bind. My center diff is programmed (by me thru a manual aftermarket controller) to progressively open as the car goes faster.

Last I did verify you have a torsen type rear diff, trans ID chart here
http://forums.nasioc.com/forums/show....php?t=2173258
go to post 1 and download the chart.

Suggest you google "torsen lsd binding" ,etc and may be that will help ID the problem. One other thing is to buy a used replacement that works and swap it in.

Or get a 2nd opinion on what the problem might be. Andrewtech is one of the world's best subie drivetrain shops. They may talk to you and offer more insight.
http://www.andrewtechautomotive.com/
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Old 08-22-2013, 07:20 PM   #15
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Just stopped by the local dealer to talk about a trade, and after pulling the Car Fax and seeing the accident he said he would need to have it thoroughly inspected, but if he had to give me a number today it would be $14-15k. I thanked him for his time and told him that he was not even in the same hemisphere as what I was thinking. He did mention that he might offer as much as $18k if the inspection came back perfect, but was worried about certifying and selling the car. More than likely, he'd fleece me and have no problem making a hefty profit by sending it to auction.

Anyway, the absolutely minimum I was willing to go was $19k, maybe a little more, but not THAT much more.

Has any one ever dealt with insurance and getting a check for devaluation? I can't believe I didn't think of this before and push for it.

Quote:
Originally Posted by mhoerath View Post
If the noise/vibration goes away when the clutch goes in, prob not a wheel bearing.

If I back up with my center diff locked, feels like something is breaking, lots of bind. My center diff is programmed (by me thru a manual aftermarket controller) to progressively open as the car goes faster.

Last I did verify you have a torsen type rear diff, trans ID chart here
http://forums.nasioc.com/forums/show....php?t=2173258
go to post 1 and download the chart.

Suggest you google "torsen lsd binding" ,etc and may be that will help ID the problem. One other thing is to buy a used replacement that works and swap it in.

Or get a 2nd opinion on what the problem might be. Andrewtech is one of the world's best subie drivetrain shops. They may talk to you and offer more insight.
http://www.andrewtechautomotive.com/
I appreciate the feedback.

Yep, knew it was a torsen from the get-go. LS gear lube was for gut check purposes only.

When you lock your center diff, does the "feels like something is breaking" come from the rear or center? I'm nearly certain my noise, feeling is coming from the rear.

I did pull the e-brake lever so that the brake light was in on the dash and it didn't change anything.

I've Googled the issue and nothing comes up that covers my problem.

I do plan to get a second opinion.
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Old 08-23-2013, 08:02 AM   #16
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Quote:
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J
When you lock your center diff, does the "feels like something is breaking" come from the rear or center?
more center.
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Old 08-28-2013, 09:48 PM   #17
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Rear diff Temp warning light comes on at approx 150c, 302f.

Just ran across it in a service manual.
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Old 08-29-2013, 04:55 PM   #18
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Rear diff Temp warning light comes on at approx 150c, 302f.

Just ran across it in a service manual.
Thanks. I wasn't very far off, and that's a good data point for knowing my diff isn't thoroughly eating itself - maybe.
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