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Discussion Starter #1
Ok, so I'm aware that it is well documented that the rear diff makes noise at or near full lock on the steering wheel going parking lot speeds stock but this is different.

I recently had the following suspension/drivetrain mods installed, mind you this sound WAS there before the mods (stock setup), just not as audible.

Whiteline RCA
Whiteline ALK - Standard
Kartboy rear outrigger bushings - race
Kartboy rear subframe lock bolts
TiC rear diff bushings - race

I got the mods installed in the middle of April 2010 and did hear an increase in noise but I haven't been driving the car frequently anymore at all so maybe I just forgot how loud it was? :lol::lol:

Anyways, basically, when the steering wheel is at or near full lock (turning into parking spots, u-turns, sharp parking lot turns) at parking lot speeds I get a relatively loud grinding/popping noise coming from the rear of the car (rear diff).

I know the mods all advertise an increase in NVH but it seems excessive.

I'm just a little worried. Like I don't want anything to be wrong. If I can get some reassurance that it's normal I'll just ignore it as I knew going in I would get an increase in drivetrain noise.
 

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what kind of diff oil are u running?
i had a bad grinding noise when i ran redline fluid in the trans and rear diff, like BAD GRINDING noise, at parking lot speeds with the steering wheel full lock.
i changed out the fluids and the grinding noise was gone.

i also have similar suspension mods as u plus more.
 

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I thought those Rear Diff "Mods" made it go away; what fluid are you running? Did you see any change in how the car acts with the rear diff lock, bushings, etc?
 

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Discussion Starter #4 (Edited)
what kind of diff oil are u running?
i had a bad grinding noise when i ran redline fluid in the trans and rear diff, like BAD GRINDING noise, at parking lot speeds with the steering wheel full lock.
i changed out the fluids and the grinding noise was gone.

i also have similar suspension mods as u plus more.
Stock fluid. It could be on its way out I guess. I'm at 277xx miles now so maybe it just needs to be changed.

I will be getting it changed out at my 30k which I plan to have done in about a month or so. Planning on using Motul fluids in the transmission and diff.

What fluid did you change to?

I thought those Rear Diff "Mods" made it go away; what fluid are you running? Did you see any change in how the car acts with the rear diff lock, bushings, etc?
Stock fluid.

They don't get rid of any noises, they actually make them louder as the vendors warn an increase in NVH. The stock bushings are soft rubber ones and these are like hard plastic. Shifts feel way smoother.

I definitely like the mods and what they did. I'm just worried that something else may be wrong.
 

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Kartboy rear outrigger bushings - race
Kartboy rear subframe lock bolts
TiC rear diff bushings - race
I had TiC install these upgrades on my '07 and have noticed the popping/grinding/banging sounds as well. I asked Tony if it increased noise levels and he said yes. I do notice these noises a lot more when the weather is hot and humid.
I am taking my car ti TiC in the next few weeks for an inspection and will point this to Tony too see if the noise is still ok.
 

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I would use the stock Subaru LSD fluid. People don't have problems with it, where as people do have problems with just about every other fluid. If you look thru different threads, for every person who says they have "XXX" fluid and it works fine, you'll find others with the same fluid and they have problems.
Every car responds differently to fluids, the rear diff especially.
 

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Discussion Starter #7
I had TiC install these upgrades on my '07 and have noticed the popping/grinding/banging sounds as well. I asked Tony if it increased noise levels and he said yes. I do notice these noises a lot more when the weather is hot and humid.
I am taking my car ti TiC in the next few weeks for an inspection and will point this to Tony too see if the noise is still ok.
It has been VERY hot and humid in DE the last month or so which is when I've noticed the noise the most.

As I said, I got these mods installed in April but it only now got very loud/noticeable.

Let me know what Tony says though. I'd be very interested in hearing TiC's feedback.

I would use the stock Subaru LSD fluid. People don't have problems with it, where as people do have problems with just about every other fluid. If you look thru different threads, for every person who says they have "XXX" fluid and it works fine, you'll find others with the same fluid and they have problems.
Every car responds differently to fluids, the rear diff especially.
Point taken. I will look into it and research some more. I will also ask IAG what they think as they will be doing my 30k.
 

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When I rode in an '04 with the "race" bushings I thought the rear diff was going to drop out of that car. It has not and that car has a lot of miles on it now. I went for the "comfort" version of the bushings as a result and do not have the same noise. I did notice an increase in gear whine, but nothing else. No pops, creaks, etc. Hope it is nothing serious.

Most of the creaks or pops from the rear have been loose sway bar link nuts in my experience, especially in parking lot manuevers. Found them loose again when I swapped in the RCE T2's a week or so ago.
 

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Discussion Starter #9
When I rode in an '04 with the "race" bushings I thought the rear diff was going to drop out of that car. It has not and that car has a lot of miles on it now. I went for the "comfort" version of the bushings as a result and do not have the same noise. I did notice an increase in gear whine, but nothing else. No pops, creaks, etc. Hope it is nothing serious.

Most of the creaks or pops from the rear have been loose sway bar link nuts in my experience, especially in parking lot manuevers. Found them loose again when I swapped in the RCE T2's a week or so ago.
Ok, so at least I'm not the only one who's had that much noise. I guess it's relatively normal? Maybe the hot/humid weather that we've been having in my area is compounding it as another member mentioned. The gear whine is also increased in my car too but most of that noise came from back when I did my short shifter and all those bushings.

I will check the rear endlink bolts though as that could be a possibility.
 

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I had motul in the rear diff and tranny. Then the rear diff started grinding and had to replace it with subaru extra s. I will be using extra s in the tranny at the next interval.
 

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the only place i could purchase extra s quarts was from fredbeans.com.
 

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im not totally sure on this, but i THINK, dealerships dont sell extra-s to the public, and the only way to order extra-s is to oder a barrel, which is good for like 5 cars?
 

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oh and correction, im running motul gear competition in the tranny and motul 90pa in the rear diff.

u should try motul its dam good.
 

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Discussion Starter #17
I have Motul in my engine and love it.

My plan was to use their fluids in the transmission and diff but some of the posts have me worried.

Maybe using the higher grade diff fluid would be better? Is 90pa at a higher quality than competition?
 

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Errrr, based on your description of the sound it sounds like your hyperplasma booster is loose and knocking around and that pretty much renders your car useless. It simply cannot be reattached. Sign your incoming rims over to me and give me your trunk. I'm sorry. we did everything we could to save her...
 

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I have Motul in my engine and love it.

My plan was to use their fluids in the transmission and diff but some of the posts have me worried.

Maybe using the higher grade diff fluid would be better? Is 90pa at a higher quality than competition?
motul's gear300 and gear competition are transmission fluids, the difference is gear competition has a high hot viscosity than gear 300

i think 75W-90 vs 75W-140

and the 90PA is for LSD/diffs

these were recommended and given to me by a great subaru suspension specialist

and alot of guys thats local to me runs motul fluids in the entire car, both for street and track. none of them has any grinding binding noise from transmission and diff.
 
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