Rear Diff noise 2007 STi (Andrewtech thoughts?) (not normal noises they tend to make)

[rxer311]

CN - bad wheel bearing causes possible rear differential damage. This is a long story. Please chime in with any experience you might have.

I have a 2007 STi that has 40000 miles on it that I have owned since new. At 30000 miles I changed out the stock fluid for Amsoil Severe Gear 75w-90 per the amsoil website and on recommendation from my tuner. Everything was great until about a month ago when my rear differential started chattering when making full lock (or close to it) turns at low speed. It was very little at first but then it started getting louder to the point that it sounds like it was moaning.

Just to be sure I changed my rear Diff fluid again (I didn't do it myself the first time so who knows). This seemd to help quiet things down for about a day. I started troubleshooting and I finally found what caused the differential noise. I had a rear wheel bearing that was absolutely shot (think AT LEAST 5mm of play on the rear wheel). Yes, it was about ready to fall off. No, it didn't make any noise (the only way I knew it was a problem was because of the rear diff sound). I can only assume that road noise masked the wheel bearing sound...it was weird because you couldn't even hear it on the highway.

So I have my wheel bearing replaced at a local shop to get ready for the autoX the comming weekend. I pick up the car with a fresh wheel bearing and not long after the rear diff noise arises again.

I get a friend to go for a ride with me who is also pretty knowledgable about cars. Remember the noise only arises when the car is at full lock or very close to it. We go to a parking lot and and do some slow figure 8's in forward and reverse and the noise gets softer and softer until it is gone. We surmised that the rear diff plates were abnormally worn and now that the rear bearing was fixed that the diff plates were able to get a normal wear pattern back into them.

Wake up the next morning to go to the autoX. Pulling out of my driveway it makes the noise again. I drive to the autoX thinking I won't take it out to race. When I get there though my friend's BMW mechanic (who also owns a subaru, this guy really knows his stuff) is there so I discuss the problem with him and he takes a ride with me. He hears the noise and he tells me that the noise doesn't concern him and that my friend and I were correct that since the bearing was fixed the diff should "work itself out". He said he hears this same sound in a bunch of M3's. He told me to "go ahead and drive the piss out of it".

I autoX, win my class. AutoX the next day, 3rd in class (the car is performing very well). Everything feels normal.

BUT...when the differential is cold it still makes noise. Not as bad as before replacing my bearing but can approach that when cold. When things warm up the noise goes away.

I am still feeling anxious about this now. Should I change my rear diff fluid again? Is my rear differential FUBARed?

Help!

Edit:
This is the gear oil I am using.

Here is where I got my info...plus the recommendation from my tuner
http://www.amsoil.com/mygarage/vehic...BARU+IMPREZA+F

This is the product...
http://www.amsoil.com/storefront/svg.aspx
"AMSOIL SEVERE GEAR® is compatible with most limited slip differentials. If limited slip differential chatter occurs, add AMSOIL Slip-Lock™ friction modifier additive."

Was thinking this might help...
http://www.amsoil.com/StoreFront/ada.aspx

* Registered users of the site do not see these ads.

[woodys77]

my friend had an 07 sti with 10,000 miles and the rear diff was loud as hell i had a wrx at the time and my diff was quite. i told him his rear diff was shot and he said all sti's were like that. i have never driven an sti before this so i agreed. now i have an 07 sti myself that now has 25,000 miles and the diff has never made a single peep. his car is still going strong as well as mine. i don't really know what all this means to you but what i gather is their most be a tolerance difference between some sti's. i wouldn't worry to much about it. try going back to subie fluid and see what happens.

[rxer311]

Originally Posted by woodys77

my friend had an 07 sti with 10,000 miles and the rear diff was loud as hell i had a wrx at the time and my diff was quite. i told him his rear diff was shot and he said all sti's were like that. i have never driven an sti before this so i agreed. now i have an 07 sti myself that now has 25,000 miles and the diff has never made a single peep. his car is still going strong as well as mine. i don't really know what all this means to you but what i gather is their most be a tolerance difference between some sti's. i wouldn't worry to much about it. try going back to subie fluid and see what happens.

Yes, My diff has always made a bit of noise but this noise is different. People can ride in my car and they will say "what the hell is that!?". This is like a moaning grinding type sound. I really don't know how else to explain it.

[Uncle Scotty]

the wrong lube in the rearend will make them loud

[rxer311]

Originally Posted by Uncle Scotty

the wrong lube in the rearend will make them loud

I understand this. I ran this fluid for almost 9000 miles with no noise. It only popped up after this bearing issue. I was thinking of using the Amsoil Friction modifier that they suggest if your diff is making noise.

Here is where I got my info...plus the recommendation from my tuner
http://www.amsoil.com/mygarage/vehic...BARU+IMPREZA+F

This is the product...
http://www.amsoil.com/storefront/svg.aspx
"AMSOIL SEVERE GEAR® is compatible with most limited slip differentials. If limited slip differential chatter occurs, add AMSOIL Slip-Lock™ friction modifier additive."

Was thinking this might help...
http://www.amsoil.com/StoreFront/ada.aspx

[Uncle Scotty]

if the noise started after the bearing issue then something associated with that must be considered as causative and explored as cureative

[rxer311]

Originally Posted by Uncle Scotty

if the noise started after the bearing issue then something associated with that must be considered as causative and explored as cureative

Thats why I started this thread

Did you read it?

[Uncle Scotty]

Originally Posted by rxer311

Thats why I started this thread

Did you read it?

there is a finite number of things that can cause this

that number is quite small

[rxer311]

Originally Posted by Uncle Scotty

there is a finite number of things that can cause this

that number is quite small

You are so helpful. Since you seem to know there are a finite number of things that cause this would you care to elaborate and let me know what they are?

And you haven't answered my question. Do you think my Diff may be toast? Should I take it to the stealership to get raped in the butt or should I let it go like the BMW tech told me to do?

[rxer311]

Bump for some real help!

[Uncle Scotty]

we dont have the car to hear the noise

asking us, here, to figure it out is not the best approach to fixing it

someone familiar with subarus, and the sti in particular, needs to hear and diagnose the issue....NOT us

this thread is a prime example of 'doing it wrong' as the REAL HELP isnt going to come from us, here


and I would NOT use ANY 'amsoil' gear lube in MY car and I believe THAT is the issue, or part of it, anyway

[rxer311]

Originally Posted by Uncle Scotty

we dont have the car to hear the noise

asking us, here, to figure it out is not the best approach to fixing it

someone familiar with subarus, and the sti in particular, needs to hear and diagnose the issue....NOT us

this thread is a prime example of 'doing it wrong' as the REAL HELP isnt going to come from us, here


and I would NOT use ANY 'amsoil' gear lube in MY car and I believe THAT is the issue, or part of it, anyway

I know of at least 2 other STIs around here running the same gear lube as I am with no problems...

I am trying to get some information here before I spend $$$$$$$$$ trying to track down a problem that may not even be a problem.

Seriously, what are the forums for if you can't ask questions.

With how you are answering my questions Uncle Scotty, it leads me to believe 1 of 3 things...

1. You don't have a clue what you are talking about
2. You know but you don't want to say, making you a jerk
3. You are just a post whore

I am simply asking for opinions and people with experience. If you don't have any then please stop posting in my thread to get your "post count" up

[AndrewtechAutomotive]

Had you considered the possibility that it isn't the rear differential at all?

Does the sound go away when you lock the center diff? Try that and report.

Phil
Andrewtech Automotive

[rxer311]

I will try that and report.

[rxer311]

Originally Posted by AndrewtechAutomotive

Had you considered the possibility that it isn't the rear differential at all?

Does the sound go away when you lock the center diff? Try that and report.

Phil
Andrewtech Automotive

I will try this tonight. When I was out doing my figure 8's I noticed that the sound got better when I opened the diff. I didn't try locking it.

[AndrewtechAutomotive]

Sounds like a DCCD issue to me. But it's hard to say for sure without driving the car.

If the noise changes with respect to the DCCD position, I'd start there.

Phil
Andrewtech Automotive

[tekfoc]

Originally Posted by rxer311

I will try this tonight. When I was out doing my figure 8's I noticed that the sound got better when I opened the diff. I didn't try locking it.

DOES the STI still have warranty if it does just take it in to the dealer for svc.

This is why I leave my drive train stock so in case of a problem Ill get it fix thrue the stealership.
my engine does have mods but I rather just put my own engine in for replacement if something was to happened .
now the suspension,brakes, differentials and dccd and gear box is very very expensive ticket this why i leave it completely stock with stock fluids.
use Subaru extra S fluid it really is very good fluid and keeps Subaru warranty people happy and your self happy .

so if you have warranty take it back for svc repair good luck let us know the outcome .

[rxer311]

Originally Posted by rxer311

I will try this tonight. When I was out doing my figure 8's I noticed that the sound got better when I opened the diff. I didn't try locking it.

I am not quite sure about this yet though, because like I said the noise goes away when the car warms up and I didn't switch my DCCD until really the sound had all but stopped when doing the figure 8's. It just seemed maybe a bit smoother driving at full lock. When I switched back to auto it still didn't make noise when warm.

The reasoning I am using for rear diff is that I had a really bad wheel bearing back there which would have been causing a lot of drag on the differential and that is where the sound seems like it is comming from confirmed by my friend and the BMW tech. I wish I had time during the week to bring it down to you . I don't trust my local subaru dealers.

[rxer311]

Originally Posted by tekfoc

DOES the STI still have warranty if it does just take it in to the dealer for svc.

This is why I leave my drive train stock so in case of a problem Ill get it fix thrue the stealership.
my engine does have mods but I rather just put my own engine in for replacement if something was to happened .
now the suspension,brakes, differentials and dccd and gear box is very very expensive ticket this why i leave it completely stock with stock fluids.
use Subaru extra S fluid it really is very good fluid and keeps Subaru warranty people happy and your self happy .

so if you have warranty take it back for svc repair good luck let us know the outcome .

I don't think they will warranty my car with all of my mods. I am sure they will say all the extra power I am making ruined my diff.

[tekfoc]

Originally Posted by rxer311

I don't think they will warranty my car with all of my mods. I am sure they will say all the extra power I am making ruined my diff.

what are your mods

[rxer311]

2007 STi

Turboback exhaust (catted), EL header, Perrin intake, fuel pump & 750cc injectors, Perrin EBCS, tuned

Whiteline swaybars, RCE yellow springs (BC coilovers going on soon)

Kartboy shifter bushings

[AndrewtechAutomotive]

Those Kartboy shifter bushings are definitely the problem.

Phil
Andrewtech Automotive

[rxer311]

Originally Posted by AndrewtechAutomotive

Those Kartboy shifter bushings are definitely the problem.

Phil
Andrewtech Automotive

Can you please explain? I trust you but I don't understand how that can be causing the noise. I don't have the short shifter...just the bushings. And I don't slam gears.

Thanks.

[rxer311]

Originally Posted by AndrewtechAutomotive

Those Kartboy shifter bushings are definitely the problem.

Phil
Andrewtech Automotive

Are these causing damage or just making noise? Back to stock?

Thanks again.

[AndrewtechAutomotive]

Haha, no. They aren't hurting anything. I was just poking fun.

It wouldn't surprise me if someone tried to deny a claim for it though!

Phil
Andrewtech Automotive