E46Fanatics

E46Fanatics (http://forum.e46fanatics.com/index.php)
-   General E46 Forum (http://forum.e46fanatics.com/forumdisplay.php?f=4)
-   -   Can anyone guess this rattle? Manual trans (http://forum.e46fanatics.com/showthread.php?t=949097)

Mccomasg09 10-07-2012 12:44 AM

Can anyone guess this rattle? Manual trans
 
Hey guys,

So it's a 2001 330ci its manual and it starts to rattle as it heats up. I believe it to be coming from the trans. My first thought is throw out bearing but after some research I heard it could be the heat shield? It is most noticeable when the AC is on? It doesn't affect performance at all.... What do y'all think it is? Throw out bearing? Heat shield? I'm pretty sure it's from the trans but if not does anyone else have any viable opinions?

Thanks in advance.

Mccomasg09 10-10-2012 12:38 AM

Haven't had a chance to get it up in the air yet but I was hoping for some input...anyone?

TitaniumCranium 10-10-2012 12:43 AM

Does it only rattle when in neutral? This sounds like the gear lash in the transmission related to the harmonic chatter caused by a lightweight flywheel.

Mccomasg09 10-10-2012 12:52 AM

That's what I thought but the previous owner bought it with no idea what's in the trans... I can tell someone was in the trans because it has a short throw shifter but idk what clutch or flywheel or even brand of short shoft kit which kind of sucks.

It doesn't do it until it is warm.
It doesn't do it when clutch is pressed.
And it is a lot louder with the AC on.

And I have an exhaust so I can't really tell if it does it when I'm not in neutral. I will check own my way to work tomoro and try and hear it, but I doubt I will even be able to hear it if it is there because of the UUC exhaust.

TitaniumCranium 10-10-2012 12:56 AM

The rattle doesn't hurt anything, just annoying. My guess is that the flywheel was replaced with a LWFW when the clutch was replaced because they're less expensive than replacing it with a factory DMF, and there is the quicker RPM climb too.

TitaniumCranium 10-10-2012 01:00 AM

The best way to explain the sound related to the LWFW is that it sounds like a can half-full of oil with a half-dozen bolts being shaken around.

The list of conditions exactly matches LWFW chatter.

Mccomasg09 10-10-2012 01:04 AM

That was my guess, this is my first bmw so idk what the average rpm climb is like... But this thing is jumpy.

So I'm guessing it has a clutch and light weight fly wheel, I just wish there was someway to tell what was in it without dropping it.

This chatter seems to be awfully loud to be natural from a lwfw, so I'm hoping there is a heat shield chatter too.

Do you think there is any chance it is a throw out bearing?

Mccomasg09 10-10-2012 01:06 AM

Wow you literally nailed it with the can of oil and nuts analogy that is spot on... Guess my new ride has a LWFW... Now I just wish I could find out what brand it is as well as the clutch and short throw shifter.

TitaniumCranium 10-10-2012 01:17 AM

The chatter is loud and usually much more noticeable when the AC is running. According to UUC you can cut down on this chatter with a mix of redline ATF/MTF. I did it for a while before I changed to straight redline MTF. It may have been a little quieter with the mix but not really sure to be honest.

You can pull back on the gear shift lever a little too and it will quiet it down a bit. if it were related to the throw-out bearing it would be more of a grinding noise than a chatter and it wouldn't matter if it was in neutral or not.

Mccomasg09 10-10-2012 01:25 AM

I read one of your previous posts and you said you can see it from under the car? Do I have to remove a shield or something like that? Is there a definitive way to tell if I have a LTFW without dropping the tranny?

TitaniumCranium 10-10-2012 01:39 AM

On the bottom of the bell housing there is a small area of material removed, probably a 1" or so for inspection and to let oil out if you have a rear main seal leak. If you had a reference from what a stock unit looked like you could compare. There might be a picture in the Bentley manual.

At any rate the DMF is steel, and nearlly all LWFW's are aluminum. The UUC flywheel is anodized blue, the Fidanza and JB Racing flywheels are bare aluminum. IIRC there is also one that is anodized purple too but can't remember who builds it. The gear ring is always steel so you have to look at the actual body of the flywheel to determine the material it's made of.

Mccomasg09 10-10-2012 01:44 AM

Thanks so much man you helped a ton...

Can you only see the gear ring from the one inch opening by the bell housing or can you see the body and determine what it is?

TitaniumCranium 10-10-2012 01:47 AM

For sure you see the gear ring but I think you can see some of the body too.

http://photos.e46fanatics.com/data/5.../DSCN05071.jpg

Look opposite the starter and you can see the largest of three slots that are in the mating surface of the bell housing. You should be able get enough of a view to see.

Mccomasg09 10-10-2012 04:22 PM

So I went to my mechanic for a check up and he seems to think it is the throw out bearing, both his lifts were blocked so we couldn't get it in the air but he said it doesn't sound consistent enough to be a LTFW. I'm going to post a link to the video here and maybe someone can tell by that and hopefully the video link works.

https://mail.google.com/mail/u/0/s/?...32-1&safe=1&zw

Also one last new symptom is it does it when in neutral and clutch isn't pressed down but if you accelerate lightly to 1k rpm it stops as well and anything higher then 1k rmp you can't hear it which makes me think LTFW. I believe it has a uuc LTFW which I thought were know for not being too loud but I could see enough to be definitive that it is uuc LTFW.

Wh33lhop 10-10-2012 05:08 PM

The noise you are experiencing is affectionately referred to as "Getrag rattle" in older BMWs. Basically the input shaft/layshaft bearings of your transmission have wear in them and when unloaded and spinning slowly (idle) they will rattle around a bit. The problem is exacerbated by a lightweight flywheel in that it provides less of a "damping" effect that would attenuate the noise.

When you press in the clutch it goes away, because the input shaft and layshaft are no longer connected to the engine and no longer spinning. It is NOT the throwout bearing as the TO bearing is only in action when you are pressing IN the clutch.

It happens on most old(ish) manual transmissioned BMWs. My 330 6 speed does the exact same thing, as well as my E30 and most other BMWs I've driven although some are louder and some are quieter. My suggestion would be to learn to live with it, unless you want to tear your trans apart and replace the bearings. A heavier flywheel would also help quiet it down a bit.

Mccomasg09 10-10-2012 08:03 PM

Quote:

Originally Posted by Wh33lhop (Post 14803568)
The noise you are experiencing is affectionately referred to as "Getrag rattle" in older BMWs. Basically the input shaft/layshaft bearings of your transmission have wear in them and when unloaded and spinning slowly (idle) they will rattle around a bit. The problem is exacerbated by a lightweight flywheel in that it provides less of a "damping" effect that would attenuate the noise.

When you press in the clutch it goes away, because the input shaft and layshaft are no longer connected to the engine and no longer spinning. It is NOT the throwout bearing as the TO bearing is only in action when you are pressing IN the clutch.

It happens on most old(ish) manual transmissioned BMWs. My 330 6 speed does the exact same thing, as well as my E30 and most other BMWs I've driven although some are louder and some are quieter. My suggestion would be to learn to live with it, unless you want to tear your trans apart and replace the bearings. A heavier flywheel would also help quiet it down a bit.

Wow thanks a lot that was some great info! Are these bearings that hard to replace if the trans is dropped? Harder then the throw out I suppose but is it a serious task? This is my first bmw and idk if I can live with it, at drive throws and parking lots people just look at me like what the hell is wrong with your car lol

Wh33lhop 10-10-2012 08:49 PM

Splitting the transmission open is not a task for the faint of heart. If it is really so loud that people are asking about it then it's likely you do have a lightweight flywheel. If you do, replace it with OEM. It shouldn't damage anything in the meantime.


All times are GMT -5. The time now is 07:33 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
(c) 1999 - 2011 performanceIX Inc - privacy policy - terms of use