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Discussion Starter #1
The car:
2009 Outback XT with a 5spd manual, 116k miles

The Problem:
When the car is cold, everything is great. After driving for 20 minutes, especially on hot days, the car will make loud popping sounds when making sharp turns. Everything is great in a straight line, but the pops when turning are LOUD and slightly rock the car. Initially I assumed it was a CV joint, so I put 2 Subaru-brand axles in the car, and went ahead and replaced the super-rusty front wheel bearings while I was at it. Now I'm $900 deep in parts and it still does it.

So here's my question: All signs point to this being a viscous coupling/center diff problem. My understanding is that all 2009 models, even with 5MT, had VDC and VDC doesn't have a viscous coupling. So could that still be the issue? I'm having a hard time finding examples of people with VDC cars that have center diff issues.

Or is it something else? Possible issue with a hub? Tone ring freaking out the AWD system? I'm a bit lost at this point, and I don't want to by a center diff or replacement transmission if that isn't the issue, and I don't know how to test it to know if it is.
 

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2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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moved to gen3 section,

those have unique things with their steering racks / suspension bits.

did you notice any leaking from the fluid filled couplings on the rack.?

_____

if it were a thing in the trans/ drive train you would have check engine lights / trans light flashing/ vdc off. (edit: MAY have)

do you get anything on the onboard diagnostic system for 2005-2009?
http://www.subaruoutback.org/forums...9-how-read-diagnostic-trouble-codes-dtcs.html

____

on my own cars: I have had issues with brake backing plates tagging moving parts when the wheels are turned sharply and the body is flexing on the suspension. (such made for a sound similar to a drum stick on a paint can kind of clunk).
 

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. . . All signs point to this being a viscous coupling/center diff problem. . . .


Yes.

The viscous coupler you mention (in regard to VDC) is probably the one in the rear differential. However, the manual transmission uses a similar viscous coupler as part of the all wheel, front-rear power distribution system. It's part of a differential (aka "center differential") built into the tail section of the transmission.

Your symptom is typical of a failing center differential viscous coupler, particularly the fact that the popping appears after having driven some time. This plus the hot weather allows the transmission to warm up (which is normal), at which point the coupler is reacting to the heat incorrectly.

Here's a thread that is for an earlier year, but the same type of symptoms. There's a suggested "test" that could be tried to confirm the problem.

Incidentally, it's important that all four tires on an AWD be the same brand, size, model and extent of tread wear. Different size tires can cause the coupler to heat up and cause the same symptoms.
 

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yep, agree with Plain, classic symptom of failing viscous locking center diff. in manual trans; seems OK stone cold, torque bind after a few minutes of warm-up. (assuming tires are identical and there's no broken rear axles or similar weird issue)
 

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Discussion Starter #5
Thanks everyone for the replies, I will do the test this evening and see what the results are.

The steering rack is bone dry. As for tires, all 4 are new-ish General Altimax tires that I put on roughly 10k miles ago. The tires before that were from the previous owner, but all 4 were the same brand and size with similar wear.

So I guess my questions now are:

- What causes this to fail? I had a 5MT Forester before this where the center diff failed (though it was the rear wheels seizing on it, and it's the front wheels on the outback) Two Subaru's in a row having the same problem makes me think I'm doing something wrong but I have no idea what it could be. Tires are replaced 4 at a time, I rotate every 9k miles, I only use Subaru brand transmission fluid... I love Subaru's but this is discouraging.

- Does anyone sell the tail section of a 5MT VDC transmission? Or is the repair for this to replace something internal?
 

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fluids?

what do you got for rear/front diff / MT trans fluid?

check them recently? swap them ever?
 

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Discussion Starter #7
fluids?

what do you got for rear/front diff / MT trans fluid?

check them recently? swap them ever?
Transmission fluid (which I understand is shared with front/center diff) was changed shortly before this problem started. I used Subaru Performance 75w90 Gear Oil that I got from the dealer. I asked for Extra-S but apparently it no longer exists.

I've never checked or serviced the rear diff.
 

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Transmission fluid (which I understand is shared with front/center diff) was changed shortly before this problem started. I used Subaru Performance 75w90 Gear Oil that I got from the dealer. I asked for Extra-S but apparently it not longer exists.

I've never checked or serviced the rear diff.
somewhere in the regular maint. it says to check that every oil change. (I have had to have a extra squirt every 15,000 miles or so,...and any outback it gets replaced every 30,000)

as any outbacks is driven "severe" as per note 3 below,...(I mean in winter, on dust, in city).

Subaru maintenance schedules and new car break-in period- 2000 through 2009, links for 2010, 2011...

open the filler hole in the top and see what there is. = full means leaking out back at you.

(important to open the filler hole BEFORE opening the drain hole. ... so if there is a problem getting the filler hole open you wont' be caught with nothing).

_____

and as this is a manual. you can't just plug in the FWD fuse like typical old school automatics.
 

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slight point of correction. The center diff contains a separate fluid. maybe it's seal has failed???

you may just have been unlucky or the previous owner abused the car with a small spare or mixed size tires in the past???
 

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2001 VDC/SC One of a Kind
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Gen 3 and up use the VTD center differential. It doesn't have the viscous clutch like up through Gen 2. I would be inclined to believe that the front diff is binding instead of allowing slip if the noise is coming from the front of the car. The VTD is 45/55 or 50/50 (front/rear) and the planetary gears within allow for a slip front to rear. Anything between the wheels on a specific axle is going to be in the front or rear differential.
 

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so nothing else can make popping sounds there? i had those sounds from strut top mounts become bad , my steering rack have movement in it so it makes popping sounds as well. steering tie rod bushings do that as well. and they not make those sounds all time so go figure that.
 

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Gen 3 and up use the VTD center differential. It doesn't have the viscous clutch like up through Gen 2. . . .

It's a 5-speed manual transmission. Pretty sure all the MTs use the mechanical center differential with integrated viscous coupler assembly. But you're right in regard to the 5EAT that the Op's XT would have if it were automatic.
 

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It's a 5-speed manual transmission. Pretty sure all the MTs use the mechanical center differential with integrated viscous coupler assembly. But you're right in regard to the 5EAT that the Op's XT would have if it were automatic.
Must not have had enough coffee this morning and ignored MT. :smile2:
 

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Discussion Starter #14
It's a 5-speed manual transmission. Pretty sure all the MTs use the mechanical center differential with integrated viscous coupler assembly. But you're right in regard to the 5EAT that the Op's XT would have if it were automatic.
But, to my understanding, 2009 was the first year they put VDT on a manual. At least, my car has a VDC 'off' button.

I don't know. I have an appointment with my mechanic. He has a viscous coupling ordered and if there's no viscous coupling in the tailcone of the transmission when he takes it off then I guess we'll go to plan B!
 

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But, to my understanding, 2009 was the first year they put VDT on a manual. At least, my car has a VDC 'off' button.

I don't know. I have an appointment with my mechanic. He has a viscous coupling ordered and if there's no viscous coupling in the tailcone of the transmission when he takes it off then I guess we'll go to plan B!
VDC is not the same as VTD. There's no problem having VDC (as is the case with your 2009) with a manual transmission. VDC makes use of the braking and engine throttle systems to control vehicle dynamics. VTD is a form of AWD front/rear torque transfer that uses a planetary center differential with a multiplate transfer clutch. The clutch is controlled by the automatic transmission control module, which a manual transmission car does not have.
 

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Discussion Starter #16
VDC is not the same as VTD. There's no problem having VDC (as is the case with your 2009) with a manual transmission. VDC makes use of the braking and engine throttle systems to control vehicle dynamics. VTD is a form of AWD front/rear torque transfer that uses a planetary center differential with a multiplate transfer clutch. The clutch is controlled by the automatic transmission control module, which a manual transmission car does not have.
Ok, that makes sense. I was under the impression VDC required VTD. IF it doesn't, then that explains some things!

Thanks!
 

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Discussion Starter #18
Did you try the test linked in post #3 to confirm if the center differential viscous coupler is malfunctioning?
No. I had a very random encounter with a subaru mechanic from the local dealership who took my car for a drive and was like "Oh yeah, your viscous coupling is toast." So that's two mechanics and everything online saying that.

So... that's all well and good but I still don't understand WHY. The car had 4 matching tires with similar tread depth when I bought it, and I replaced them with 4 brand new tires. Subaru brand tranny fluid, regular tire rotations... and I'm rewarded with a cooked center diff? Man that feels wrong.
 

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why did I have 2nd gear self-destruct in my 5spd? under 70k miles - NO power mods.

$2000 trans rebuild
 

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No. I had a very random encounter with a subaru mechanic from the local dealership who took my car for a drive and was like "Oh yeah, your viscous coupling is toast." So that's two mechanics and everything online saying that.
Guess that's it . . .

So... that's all well and good but I still don't understand WHY. The car had 4 matching tires with similar tread depth when I bought it, and I replaced them with 4 brand new tires. Subaru brand tranny fluid, regular tire rotations... and I'm rewarded with a cooked center diff? Man that feels wrong.

The car has a previous owner (or owners) in its 100+k mile history. Perhaps at one time the car was towed two wheels up, or driven for a long time with odd size tires. Do that and the special silicone fluid in the sealed viscous coupler will cook. (Or, use the handbrake to control the rear wheels for wheelies -- that'll make quick work of the coupler too.) It might not initially be locked up, but it could be thicker than it should be to start with. With continued driving (not necessarily being towed two up), and especially if there's odd size tires on the car, the already partially gelled fluid will heat up due to heat in the transmission and just regular shearing when cornering etc. As in cooking it could be a long "simmer", until it eventually has changed enough that just a small amount of heat causes it to bind the coupler plates together like a glue. (The absence of torque bind when cold was also the symptom in the linked thread.)

A couple of years ago I got hold of a center differential that had been pulled from a 2010 Forester, for much the same reason. I couldn't turn the side gear relative to the differential housing because of the binding. When disassembled, I found the special silicone oil in the sealed coupler to be black and thick, instead of honey-colored and fluid. My photos and comments can be accessed on Photobucket using

ppphttp://s1008.photobucket.com/user/plainom2/library/MT%20CENTER%20DIFF%20PRESENTATION?sort=6&page=1 .

Copy the above address, paste in a separate browser tab or page, remove the ppp at the beginning, and then go. When Photobucket opens, type in (copy and paste doesn't always work) the password: centredifferential . The View Album box below should turn blue. Click on it. That should open a gallery of slides. Click Slideshow at the upper right. The slides should then appear one by one in the proper order. Press the Pause button at the lower left, and use the arrows on the right and left edges to change slides manually.
 
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