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Old 09-07-2012, 04:01 PM   #1
giosoccer20
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Default Prominent metallic clunking/knocking/clicking sound when making slow turns

'99 2.5 RS, 108k miles. I just replaced the CV joints in hopes of solving the problem, bu they made no difference. It's not even just a sound, you can feel the car jerking slightly with every clunking sound. It only happens at slow parking lot speeds when turning either direction. I also just had my mechanic put on the original rims and tires because we had a suspicion that the spacers were bad, but again, the problem wasn't solved. I bought the car as a fixer-upper, it was sitting for 3 years up until a month ago, when i bought it. Everything else is now great on the car, as I've fixed it all, and this is the only problem left. I'm hoping it has nothing to do with the transmission. My mechanic has been saying that maybe it's the transfer case, idk. The next thing I want to do is change the front diff oil, which would probably be a smart move. Any ideas? Could the diff just be really messed up? I've never noticed the problem while driving at normal speeds or going around corners fast. I've felt the diffs working fine during driving based off of how the car performs. I haven't gotten any doubts that anything is wrong with the car or tranny or diffs while driving on windy backroads. Any input would be greatly appreciated! Thanks

OH and one thing I've noticed is that when I start the car up in the morning and pull out of my driveway, it doesn't have that problem at all...if it were end links it would do it all the time wouldn't it? The sound starts after it's been driven for like 5 minutes or so. Makes me think it's the differential or oil or something after it comes up to operation temp? i'm clueless
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Old 09-07-2012, 04:11 PM   #2
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just doing a bit more research, and it seems like a f**ked center differential...and I think I know why. The previous owner had put on 17inch rtech wheels on 215 section rubber...that dumb*ss. I've been reading that driving even on an under-inflated tire for too long can mess up the center diff, let alone 4 wheels which are too large. I had them taken off today, but I guess it's too late for that...there is no way on earth that I can afford a new differential, i'm broke
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Old 09-07-2012, 04:57 PM   #3
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oh and the thing is, it does the same exact thing when it's out of gear, so that makes me think it isn't the diff, since it's coasting in neutral?
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Old 09-07-2012, 05:26 PM   #4
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It's almost certainly the center differential. Binding/popping in tight turns at slows speeds is the classic symptom of a failed viscous unit. About $400 ish for the phase II unit and a half day of work for a decent hobby mechanic. The phase II center diff unit is about $400, not sure if 99 is phase I or II as far as the transmission goes.

check the transmission/driveline forum for more info about this topic and how to/tips if you are going to diy. It is relatively easy.
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Old 09-07-2012, 05:30 PM   #5
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Quote:
Originally Posted by RaceFaceXC View Post
It's almost certainly the center differential. Binding/popping in tight turns at slows speeds is the classic symptom of a failed viscous unit. About $400 ish for the phase II unit and a half day of work for a decent hobby mechanic. The phase II center diff unit is about $400, not sure if 99 is phase I or II as far as the transmission goes.

check the transmission/driveline forum for more info about this topic and how to/tips if you are going to diy. It is relatively easy.
but what about the fact that it does it while it's out of gear? there's no power going to the differentials for it to be sorting out..?
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Old 09-07-2012, 08:26 PM   #6
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completely forgot to mention this additional bit of info also..I've noticed that the problem doesn't really exist when it is raining. so what on earth could that possibly mean? I need some more input pleaseeeee, this problem is driving me crazy
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Old 09-08-2012, 10:56 AM   #7
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There is no tq being applied to the input (engine side) of the diff, but it still has to slip to make up for differences in wheel speeds. The diff doesn't transfer tq like a drive shaft, it allows the two sides to rotate at different speeds while still being coupled.

You don't notice it in the rain (or on other low friction surfaces) because the tires can slip a bit so the diff doesn't have to. The tires offer less resistance than the diff in those cases.

I have seen this exact thing happen twice first hand. Both on 04 RS's. When driving them in the dirt/grass they didn't seem to have any problem but on dry pavement they creaked and popped. If you watch the wheels when you make these slow sharp turns you can actually see them bind up and then release.

You need to go search the correct sub forum if you are not convinced. There will be scores of threads/posts about exactly this topic.
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Old 09-08-2012, 11:29 AM   #8
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Some times a simple fluid change will fix that, if it is an auto change it with valvoline max life that usually works and it is cheaper to try than just changing it.
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Old 09-08-2012, 12:03 PM   #9
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Quote:
Originally Posted by RaceFaceXC View Post
There is no tq being applied to the input (engine side) of the diff, but it still has to slip to make up for differences in wheel speeds. The diff doesn't transfer tq like a drive shaft, it allows the two sides to rotate at different speeds while still being coupled.

You don't notice it in the rain (or on other low friction surfaces) because the tires can slip a bit so the diff doesn't have to. The tires offer less resistance than the diff in those cases.

I have seen this exact thing happen twice first hand. Both on 04 RS's. When driving them in the dirt/grass they didn't seem to have any problem but on dry pavement they creaked and popped. If you watch the wheels when you make these slow sharp turns you can actually see them bind up and then release.

You need to go search the correct sub forum if you are not convinced. There will be scores of threads/posts about exactly this topic.
Yeah im convinced. So what needs to be changed if the diff oil change doesnt help?
The center differential right? I bought the car with 108k miles on it and before i had bought it, it was sitting for 3 years, so the oil should definietly have been changed right? I mean, tge guy i bought it from was an honest man and said the car never had any problems other than the blown head gasket which caused him to stop drivkng it
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Old 09-08-2012, 12:05 PM   #10
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Originally Posted by mod maniac View Post
Some times a simple fluid change will fix that, if it is an auto change it with valvoline max life that usually works and it is cheaper to try than just changing it.
No its a 99 2.5 manual. So what oil do i need? And is it the front differential oil i need to change or what? I need like exact terms lol
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Old 09-08-2012, 07:37 PM   #11
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Quote:
Originally Posted by giosoccer20

Yeah im convinced. So what needs to be changed if the diff oil change doesnt help?
The center differential right? I bought the car with 108k miles on it and before i had bought it, it was sitting for 3 years, so the oil should definietly have been changed right? I mean, tge guy i bought it from was an honest man and said the car never had any problems other than the blown head gasket which caused him to stop drivkng it
The center diff is bathed in the transmission gear oil. However, the gear oil does not do anything except lubricate the bearings that the diff rides on. The center diff is a viscous unit that is sealed. Inside there is a silicone based fluid that changes viscosity when the two sides of the diff are moving relative to each other. If that fluid is over heated or fails for another reason it loses its ability to work properly and it will provide resistance and then slip suddenly. That is the binding and popping you feel and hear.

While a fluid change may help, I highly doubt it will make a noticeable difference on a manual transmission center diff. On an auto, the transmission fluid provides the lubrication for the clutch pack inside the diff, but that is an entirely different type of differential. Yours does not have clutches and plates that are bathed in ATF.

Quote:
Originally Posted by giosoccer20

No its a 99 2.5 manual. So what oil do i need? And is it the front differential oil i need to change or what? I need like exact terms lol
The front diff is an open differential so unless it is damaged severely like teeth broken or something, I should not cause this problem. It is also lubricated with the transmission gear oil.

The rear diff is a viscous unit similar to the center diff and it had its own gear oil. It would not be a bad idea to change that oil if it had been sitting for 3 years, but like I said before, the gear oil does not act as a tq transfer medium so it only lubricated the ring/pinion and the bearings.
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Old 09-08-2012, 08:19 PM   #12
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Quote:
Originally Posted by RaceFaceXC View Post
The center diff is bathed in the transmission gear oil. However, the gear oil does not do anything except lubricate the bearings that the diff rides on. The center diff is a viscous unit that is sealed. Inside there is a silicone based fluid that changes viscosity when the two sides of the diff are moving relative to each other. If that fluid is over heated or fails for another reason it loses its ability to work properly and it will provide resistance and then slip suddenly. That is the binding and popping you feel and hear.

While a fluid change may help, I highly doubt it will make a noticeable difference on a manual transmission center diff. On an auto, the transmission fluid provides the lubrication for the clutch pack inside the diff, but that is an entirely different type of differential. Yours does not have clutches and plates that are bathed in ATF.



The front diff is an open differential so unless it is damaged severely like teeth broken or something, I should not cause this problem. It is also lubricated with the transmission gear oil.

The rear diff is a viscous unit similar to the center diff and it had its own gear oil. It would not be a bad idea to change that oil if it had been sitting for 3 years, but like I said before, the gear oil does not act as a tq transfer medium so it only lubricated the ring/pinion and the bearings.
Well the problem starts after like 10-15 min of driving, so could it be that the fluid is not doing its job for some reason and is causing overheating/malfunction?

So, there are 3 differentials? rear, center, and front? I'm sorry like I drove a 95 mustang 5.0 before this, which I'm sure you know is the most simple car on this planet haha.

If I went to change the fluid in hopes of solving the problem, I'd want to change the center differential fluid then right? Thanks a lot for your input, I greatly appreciate it.

Oh and one last thing, what fluid do i need? Is is it the same as the transmission fluid? I heard some people say that it is a different viscosity and very thick. like 80w90 or something?
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Old 09-08-2012, 10:35 PM   #13
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Quote:
Originally Posted by giosoccer20 View Post
My mechanic has been saying that maybe it's the transfer case, idk.
Subarus don't have transfer cases (well, not since the late 80s at least), so I'm not sure I would trust that mechanic to help much with this.

Quote:
Originally Posted by giosoccer20 View Post
just doing a bit more research, and it seems like a f**ked center differential...and I think I know why. The previous owner had put on 17inch rtech wheels on 215 section rubber...that dumb*ss. I've been reading that driving even on an under-inflated tire for too long can mess up the center diff, let alone 4 wheels which are too large.
Uhhhhh... no. Not sure what you've been reading that would make you think that 17" wheels with 215s are "too large" or would somehow cause a diff to fail, but that's not the problem, and the previous owner isn't a dumbass.

Quote:
Originally Posted by giosoccer20 View Post
Well the problem starts after like 10-15 min of driving, so could it be that the fluid is not doing its job for some reason and is causing overheating/malfunction?
That seems like the best guess at this point.

Quote:
Originally Posted by giosoccer20 View Post
So, there are 3 differentials? rear, center, and front?
Yes.

Quote:
Originally Posted by giosoccer20 View Post
If I went to change the fluid in hopes of solving the problem, I'd want to change the center differential fluid then right? Thanks a lot for your input, I greatly appreciate it.
Yes, although as RaceFace already pointed out, it's not very likely that it will make a difference.

Quote:
Originally Posted by giosoccer20 View Post
Oh and one last thing, what fluid do i need? Is is it the same as the transmission fluid? I heard some people say that it is a different viscosity and very thick. like 80w90 or something?
75W90.

If the fluid change doesn't fix the problem then I would guess the most cost effective fix will be to just swap the tranny with a used known good tranny. If you update your profile to show where you're located you may be able to find some assistance from local Subie enthusiasts who could help you swap the tranny for free (or the cost of some beverages and snacks).
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Old 09-09-2012, 08:31 AM   #14
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Quote:
Originally Posted by Patrick Olsen View Post
Subarus don't have transfer cases (well, not since the late 80s at least), so I'm not sure I would trust that mechanic to help much with this.


Uhhhhh... no. Not sure what you've been reading that would make you think that 17" wheels with 215s are "too large" or would somehow cause a diff to fail, but that's not the problem, and the previous owner isn't a dumbass.


That seems like the best guess at this point.


Yes.


Yes, although as RaceFace already pointed out, it's not very likely that it will make a difference.


75W90.

If the fluid change doesn't fix the problem then I would guess the most cost effective fix will be to just swap the tranny with a used known good tranny. If you update your profile to show where you're located you may be able to find some assistance from local Subie enthusiasts who could help you swap the tranny for free (or the cost of some beverages and snacks).
Is such a thing possible...for free?? Wouldn't a used but good center diff be less expensive than an entire tranny though?
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Old 09-09-2012, 11:28 AM   #15
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*Update* i just took it to a local shop to get the center diff oil changed...and they're like we couldnt because there is no access point on the center differential...before I brought it in i had called and was telling them that the oil is shared from the transmission with the differential and the woman is like noo no no you are mixing it up, they just use the same oil but are separate from another. they're completely wrong aren't they? draining the tranny oil drains the center diff and vice versa, new oil will refresh the diff also.
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Old 09-09-2012, 11:39 AM   #16
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anyways, I've been trying to find a new center differential to just swap it out, and I can't find anything for my car. any ideas?
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Old 09-09-2012, 01:48 PM   #17
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Is such a thing possible...for free?? Wouldn't a used but good center diff be less expensive than an entire tranny though?
The swapping of the tranny would be free, not the tranny itself. My point is that you can save yourself all the labor costs by doing it yourself or with assistance rather than paying a shop to do it.

You can find plenty of used transmissions - here, rs25.com, ebay, etc. When you find a known good used center diff, let me know.

Quote:
Originally Posted by giosoccer20 View Post
*Update* i just took it to a local shop to get the center diff oil changed...and they're like we couldnt because there is no access point on the center differential...before I brought it in i had called and was telling them that the oil is shared from the transmission with the differential and the woman is like noo no no you are mixing it up, they just use the same oil but are separate from another. they're completely wrong aren't they? draining the tranny oil drains the center diff and vice versa, new oil will refresh the diff also.
So, this shop thinks the center diff fluid is separate from the transmission fluid, but there's no way to drain or fill the center diff? Sounds like a great shop! You might want to consider going somewhere else, like the dealer, or your own driveway/garage. Draining and filling the transmission is easier than an oil change (less fluid, and you don't even have to worry about a filter).
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Old 09-09-2012, 02:25 PM   #18
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As long as you can get the plug out without destroying it.
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Old 09-09-2012, 03:42 PM   #19
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Quote:
Originally Posted by Patrick Olsen View Post
The swapping of the tranny would be free, not the tranny itself. My point is that you can save yourself all the labor costs by doing it yourself or with assistance rather than paying a shop to do it.

You can find plenty of used transmissions - here, rs25.com, ebay, etc. When you find a known good used center diff, let me know.


So, this shop thinks the center diff fluid is separate from the transmission fluid, but there's no way to drain or fill the center diff? Sounds like a great shop! You might want to consider going somewhere else, like the dealer, or your own driveway/garage. Draining and filling the transmission is easier than an oil change (less fluid, and you don't even have to worry about a filter).
yeah i haven't seen a single OEM differential yet...new or used. thank the baby jesus that I found a private subaru specialist shop yesterday 3 min away from me. I'll me taking the car there tomorrow
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