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Old 04-30-2014, 07:35 PM   #1
Turnyface
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Default Transmission Noise (Lightweight Flywheel?)


Long story short:
Blew 5MT transmission. Rebuilt by reputable shop with Legacy GT gears. Installed new Exedy OEM clutch and ACT flywheel.

I got the car back and now when I decel in gear, I get this weird grinding noise. Any idea what it is? Is it the Lightweight Flywheel?

1. Only happens in gear (noise completely disappears when I push the clutch in and/or shift and roll in neutral.

2. Shop said old bearings were good and they ised the old bearings when they rebuilt. New 1-4 gears and new synchros were put into the tranny.

I've read many threads and watched videos. Seems like it's very similar to the "Crude Transmission" thread.

http://forums.nasioc.com/forums/show....php?t=1097682

Please HALP!
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Old 05-01-2014, 11:31 AM   #2
Turnyface
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Ideas?
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Old 05-01-2014, 12:31 PM   #3
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It is sort of hard to hear over video, but I would guess it's what you are suspecting. I have this "crude decel noise" as well because I added so many performance bushings, mounts, etc along with an upgraded exedy clutch. My flywheel is oem(did this to AVOID the noise), but I still get the decel grumble in certain gears. Inside my clutch and pressure plate box from exedy they supplied a bunch of literature, one sheet mentioned that hearing deceleration noise is quite normal and is generally accepted in the high performance field
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Old 05-02-2014, 11:40 PM   #4
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Thanks for the reply. Sorry about the video audio - I thought it was more audible, but I guess I know what I'm listening for.

I also have all the harder bushings installed, which probably doesn't help with noise (but damn, shifting feels excellent!).

I'll just live with it. Its not like I'm driving a Buick around town.
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Old 05-03-2014, 12:19 AM   #5
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Bad pilot bearing.. you'll see wuat im saying.. mine was bad out of the box, 50mi and it came back out..

http://forums.nasioc.com/forums/show....php?t=2354905
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Old 05-03-2014, 06:56 PM   #6
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Originally Posted by Aaron'z 2.5RS View Post
Bad pilot bearing.. you'll see wuat im saying.. mine was bad out of the box, 50mi and it came back out..

http://forums.nasioc.com/forums/show....php?t=2354905
I'll look into this, thanks.

Is the faulty bearing (which was new when replaced) an issue for drivability, or is it just a nuisance?
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Old 05-03-2014, 09:55 PM   #7
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I also have the lgt 1-4 gears,with group N motor mounts, pitch stop, and tranny mounts, upgraded tranny crossmember and shifter bushings in my bugeye.

I have an oem clutch and flywheel and I have the same decel noise.

The gears are known for a little extra noise and any upgraded bushings or flywheel will amplify it.

I've put around 6500 miles on my new setup and the noise will improve slightly over time.

You'll get used to it.
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Old 05-11-2014, 10:06 AM   #8
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Let's bump this.

I did some investigating last night because I was certain the sound was still coming from the rear. I ended up hearing the exact same grinding sound where the rear diff connects to the driveshaft.

Here's a video:

Now here's the kicker. I'm 100% sure its not the rear differential. Why?

1. I was having the same issue before and it was recommended that I replace the rear differential.
http://forums.nasioc.com/forums/show....php?t=2620427

2. I bought a used one from a vendor who tested it and said it was in perfect working condition. The sound didn't disappear.

3. I put my old differential on another WRX and the sound was nonexistent.

My thoughts are the driveshaft. Would it make this sound if it's damaged (only at 2500-4500 RPM)? If not, what else could it be?
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Old 05-11-2014, 10:58 PM   #9
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Another thought.....the sound only happens in gear. If it truly is the driveshaft, wouldn't I hear it when I am coasting in neutral?

Maybe the connection between the tranny and driveshaft is bad? Is there a bearing or something on the other end of the driveshaft that could be bad and causing a sound that's resonating through the driveshaft to where it connects to the rear differential?

Funny thing is though, that there's no sound coming from under the transmission or driveshaft towards the front of the car.

Please help!
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Old 05-12-2014, 04:16 AM   #10
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Quote:
Originally Posted by Turnyface View Post
Another thought.....the sound only happens in gear. If it truly is the driveshaft, wouldn't I hear it when I am coasting in neutral?

Maybe the connection between the tranny and driveshaft is bad? Is there a bearing or something on the other end of the driveshaft that could be bad and causing a sound that's resonating through the driveshaft to where it connects to the rear differential?

Funny thing is though, that there's no sound coming from under the transmission or driveshaft towards the front of the car.

Please help!
That sounds like a center diff problem, or the driveshaft carrier bearing is bad. Can you tell if there is any slop in the driveshaft by pushing on it in different directions?
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Old 05-12-2014, 09:30 AM   #11
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Originally Posted by 2Fast4U1DAY View Post
That sounds like a center diff problem, or the driveshaft carrier bearing is bad. Can you tell if there is any slop in the driveshaft by pushing on it in different directions?
There is very minimal movement in the driveshaft when I try pushing it. It feels pretty solid.

So maybe the center diff?

If it is the center diff, would it make sense that the sound is showing up where the driveshaft connects to the rear diff?
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Old 05-12-2014, 09:39 AM   #12
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I had the same issues and thought the SAME thing...

It was the 20$ pilot bearing. .

Hell I was looking for a new driveshaft and rear diff, I thought for sure the carrier bearing went...

Not
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Old 05-12-2014, 09:43 AM   #13
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Quote:
Originally Posted by Turnyface View Post

I'll look into this, thanks.

Is the faulty bearing (which was new when replaced) an issue for drivability, or is it just a nuisance?
If you follow my link you will see the bearing pissed grease/oil over the FW.. not sure about you but that spells drivability issues to me once the clutch is good and contaminated. . Jus sayin
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Old 05-12-2014, 10:50 AM   #14
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Originally Posted by Aaron'z 2.5RS View Post
If you follow my link you will see the bearing pissed grease/oil over the FW.. not sure about you but that spells drivability issues to me once the clutch is good and contaminated. . Jus sayin
Even though the pilot bearing is brand new? I just had the clutch and flywheel done with the tranny rebulid....
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Old 05-12-2014, 10:59 AM   #15
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Quote:
Originally Posted by Turnyface View Post

Even though the pilot bearing is brand new? I just had the clutch and flywheel done with the tranny rebulid....
Aaron hopped in on a thread a while back with pics that had oil slung all over the PP FW and clutch disc IIRC, and it was the pilot bearing. His was brandy new too.
Its cheaper and easier than digging into the unit itself, so maybe crack the engine/trans apart and see whats goin on in there? If its not the pilot bearing it sounds like its going to be internal and you are going to be yanking the trans anyway...

Who did the rebuild?

If you pull it apart and everythings kosher up front with the clutch assembly and pilot bearing, try dropping the Driveshaft and see what that carrier bearing sounds like. If its not one of the two its going to be internal and I would start looking into sending it to Andrewtech. Thats the only shop I would trust with my trans...
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Old 05-12-2014, 11:05 AM   #16
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Quote:
Originally Posted by 2Fast4U1DAY View Post
Aaron hopped in on a thread a while back with pics that had oil slung all over the PP FW and clutch disc IIRC, and it was the pilot bearing. His was brandy new too.
Its cheaper and easier than digging into the unit itself, so maybe crack the engine/trans apart and see whats goin on in there? If its not the pilot bearing it sounds like its going to be internal and you are going to be yanking the trans anyway...

Who did the rebuild?

If you pull it apart and everythings kosher up front with the clutch assembly and pilot bearing, try dropping the Driveshaft and see what that carrier bearing sounds like. If its not one of the two its going to be internal and I would start looking into sending it to Andrewtech. Thats the only shop I would trust with my trans...
I had a local subaru performance shop rebuild the tranny. I guess I'll start with the bearing and move on from there.....damn.
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Old 05-13-2014, 09:40 AM   #17
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The pics of the flywheel from my thread where after about 50mi... its resonated so bad down the drivetrain that the driveshaft carrier bearing started losing some grease.. why I thought it was the rear diff at one point..

I can accept a lot of noises, but rock-crusher.. no thanks im not that hardcore

I learned a lot.. like pull the motor.. so much easier to hang it off a hoist than to muscle the trans back up into position (unless you have a lift)
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Old 05-13-2014, 08:01 PM   #18
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Do you hear it all the time or only when you let off the gas while you are still in gear?
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Old 05-13-2014, 08:43 PM   #19
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Do you hear it all the time or only when you let off the gas while you are still in gear?
Only decelerating in gear, which makes me think it's not the driveshaft or center differential.

I ordered an OEM pilot bearing, so I'll see of this fixes the issue.
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Old 05-13-2014, 10:18 PM   #20
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I had the same noise in my swapped rs, it's the lwfw, I researched it a bit and found a few threads on here where people had the same issue, one of the threads had a video with the same noise, one guy tried switching back to the oem flywheel and it fixed the noise . it's been a while so I forget what searches I found them under.
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Old 05-13-2014, 11:14 PM   #21
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Yeah, it seems to be pretty common with these cars. Google "wrx decelerating noise", you will find a lot of other people have the same problem. It seems to happen more ofter with lightweight flywheel.

I have the same noise on my car since I bought it. I have put 60 000 km on it and the trans works as well as the day that I got it, it has not gotten worse.

One thing that you can do to reduce the noise is to put 4-5 more PSI in the front tires.

I changed the clutch last winter and I replace the pilot bearing at the same time. It did not make a difference.
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Old 05-14-2014, 09:14 AM   #22
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I had the same noise in my swapped rs, it's the lwfw, I researched it a bit and found a few threads on here where people had the same issue, one of the threads had a video with the same noise, one guy tried switching back to the oem flywheel and it fixed the noise . it's been a while so I forget what searches I found them under.
So "its the LWFW" based on a couple of searches you've done... and you just let the OBVIOUS issues go "because other people said it was ok"

You're pretty confident for someone that's only dont a couple of searches, shrugged thier shoilders and gave up
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Old 05-14-2014, 10:43 AM   #23
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Originally Posted by Aaron'z 2.5RS View Post

So "its the LWFW" based on a couple of searches you've done... and you just let the OBVIOUS issues go "because other people said it was ok"

You're pretty confident for someone that's only dont a couple of searches, shrugged thier shoilders and gave up
No worries man. I'm going to see what's up with the pilot bearing.
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Old 05-15-2014, 12:22 PM   #24
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I had a similar noise, wasn't bad. Here's my quick story.

Pulled trans, found pilot bearing frozen solid. So I swapped everything.

OEM flywheel (pilot was in it)
OEM Exedy clutch
Snout repair kit w/oversized throw out
Drained the redline 75/90ns replaced it with Motul 300

Guess what? Decel noise was even worse after!! :-/

Drained the Motul 300, went back to Redline. Noise is greatly reduced, keep in mind I have every poly bush TiC offers and both motor/trans Group N mounts.

All is balanced in the world.
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Old 05-15-2014, 06:29 PM   #25
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Quote:
Originally Posted by Aaron'z 2.5RS View Post
So "its the LWFW" based on a couple of searches you've done... and you just let the OBVIOUS issues go "because other people said it was ok" You're pretty confident for someone that's only dont a couple of searches, shrugged thier shoilders and gave up
actually since I'm a seasoned bmw master tech I really didn't care about a noise that was clearly brought about by modifying oem drivetrain components and since after 50k miles of driving with no change it was pretty clear that nothing was really wrong, just normal harmonics of the trans which now had a flywheel that was 10lbs lighter. the only reason I stumbled on the cause was that I was curious if there were any easy fixes. turns out there is, put the oem flywheel back on
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