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Popping when turning and it's not a CV joint

9K views 24 replies 8 participants last post by  fcsr37 
#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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#2 ·
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).
 
#3 ·
. . . 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.
 
#4 ·
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)
 
#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?
 
#6 ·
fluids?

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

check them recently? swap them ever?
 
#7 ·
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.
 
#10 ·
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.
 
#15 ·
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.
 
#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!
 
#11 ·
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.
 
#18 ·
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.
 
#21 ·
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#22 ·
So yesterday I took my car to the dealer to be aligned. I had been procrastinating doing it after installing control arms, axles, and wheel bearings because I kept thinking the problem was somewhere in those parts. Knowing now that it's not, I went ahead and got it aligned. It was WAY out. Both front tires were at -0.51° toe in the front, and one rear tire was at -.21° toe. It's amazing how different/better the car drives with that fixed!

So my question is... is it possible that alignment can cause the car to think something is slipping and kill the center diff? Just grasping at straws as to why this has happened.

Also the dealer was like "Hey, bad news, you need a center diff" and I was like "I know, I'm working on it." They also let me know that my clutch pedal isn't supposed to be that stiff and I'll need a clutch soon. *sigh*
 
#23 ·
. . . So my question is... is it possible that alignment can cause the car to think something is slipping and kill the center diff? Just grasping at straws as to why this has happened. . .
There's no "thinking" involved in the MT's totally mechanical center differential viscous coupler. It (normally) works on the basis of movement between the coupler plates, and shearing of the special fluid as a result of the relative movement. The fluid is designed to accommodate normal differences between the rotational speed of the front and rear drives so that torque bind doesn't build up when turning corners or parking. It's only when the shearing is significant, and longer lasting, that the fluid is supposed to heat up and starts to bind the plates, e.g. when one wheel is spinning while the others are going much more slowly, or not turning at all. When the shearing stops, the fluid cools and returns to it's original state.

Alignment is not likely to cause the front and rear drives to turn at sufficiently different rates to cause the fluid to heat up for extended periods, which can cause it to degrade, unless it's severe enough. In the latter case, I would imagine the car would be exhibiting other, very noticeable symptoms, such as wheel bounce, pulling and perhaps even scraping sounds.
 
#25 ·
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.
This is an old thread, I know, you probably don't care about this any more. The guys that wrote about the viscous coupler are totally correct: exactly the same thing happened with my 2010 Subaru 5 speed. the VC is in the center differential: front to back differential; it contains a bunch of corrugated disks on a shaft, the even ones connected to the shaft; the odd ones to the casing; and it is filled with this heavy sticky silicone jelly, about 1000 weight. When the shaft turns it transmits a certain amount of power through the jelly, to the casing and so, to the rear wheels, but front and rear wheels can turn independently also. Now: when this jelly gets hot, it gets hard! (The opposite of most oils.) If the front wheel spins (say, on ice) then these disks spin relative to each other and the stuff heats up real fast, gets hard, and then the front and rear wheels are locked, so you can proceed off the ice. Here is the problem: when it gets old, or abused (such as towing the car by two wheels) then the jelly loses its flexibility and it hardens at too low a temperature. So it's OK in the morning but you drive the car on the highway for a while, the VC gets pretty hot, the jelly hardens, and the front and rear wheels are locked. You stop and make a turn on pavement and the wheels don't slip properly, click click click! Most mechanics, even transmission specialists, do not understand this. It took me days of searching through forums to figure all this out.

Even with proper care the VC jelly starts to deteriorate after 150,000 miles or so; mine went at 110,000 miles, probably because I did a lot of highway driving. When Subaru warns you about irregularly worn tires, or about towing on 2 wheels, this is what they're talking about: you will force the VC to rotate quickly, overheating the jelly over a long period of time, and degrading it.

Subaru doesn't make VC any more but you can still buy them on Amazon through authorized Subaru dealers, about $500. It's a cute little thing, something smaller than a big 7-up bottle. The problem is that replacing it involves removing the muffler and a bunch of other stuff (but not the transmission!). This cost me about $1000 in labor: muffler bolts were rusted and broke, and so on, but my mechanic popped the new VC in, and the Subaru runs like new! Subaru dealers will want about $2500 to change the VC and probably ask for more once they run into trouble with rusted bolts.
 
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