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**Brew** · 09-20-2005, 08:10 PM

Sounds like a bad throwout bearing.

**Eric Giles** · 09-20-2005, 08:57 PM

Originally posted by Brew

Sounds like a bad throwout bearing.

A bad throwout bearing should only make noise when the clutch pedal is pushed in, since that is the only time it is actually doing anything.

It sounds like the typical Getrag manual transmission knocking which is usually either caused by 'gear slap' or a worn input shaft bearing (from what I have been told).

I would first change the transmission fluid with Redline MTL-that might help quiet it down a bit. If not, then a transmission rebuild or replacement is in order-that is if the noise bothers you that much.

**Brew** · 09-20-2005, 09:13 PM

Originally posted by Eric Giles

Originally posted by Brew

Sounds like a bad throwout bearing.

A bad throwout bearing should only make noise when the clutch pedal is pushed in, since that is the only time it is actually doing anything.

It sounds like the typical Getrag manual transmission knocking which is usually either caused by 'gear slap' or a worn input shaft bearing (from what I have been told).

I would first change the transmission fluid with Redline MTL-that might help quiet it down a bit. If not, then a transmission rebuild or replacement is in order-that is if the noise bothers you that much.

Dammit, I can't believe I screwed that up. :oops: Clutch pedal applied, clutch disengaged!

So yeah, check out that input shaft bearing. :up:

**BahnE30** · 09-21-2005, 09:45 AM

the release bearing my me dirty or worn, if it goes away when the clutch pedal is depressed do what everyone says replace with redline MTL it helps a lot of things in the getrag for sure

**EtaSport** · 09-21-2005, 12:42 PM

Okay, thanks for the input. Dont suppose too many transmissions see 400,000 miles and not make any noise. I am really regretting driving this car in the city, hard on the poor thing.

**James Crivellone** · 09-21-2005, 01:00 PM

mine has always made a small chatter when the clutch is out in neutral.

Fluid is nice and clean, so I just shrug it off.

**joshh** · 09-21-2005, 01:35 PM

That's correct. The bearing makes noise when the clutch pedal is not pushed down. As soon as you engage it, it stops making noise. But usually the throw out bearing has a high pitched sweel not clunking.
Brew was right with his first post.

**Eric Giles** · 09-21-2005, 02:50 PM

Originally posted by joshh

That's correct. The bearing makes noise when the clutch pedal is not pushed down. As soon as you engage it, it stops making noise. But usually the throw out bearing has a high pitched sweel not clunking.
Brew was right with his first post.

No, once again, that is not correct. Brew realized his error in the response to my post and agreed that it is not the throwout bearing making the noise.

The only time a throwout bearing can make noise is when the clutch pedal is pushed in. When the clutch pedal is not being pressed, the throwout bearing is just sitting there on the input shaft of the transmission and has basically no load on it at all. When the clutch pedal is pushed in, the release fork pushes the throwout bearing against the pressure plate/clutch assembly to disengage the clutch. This is the only time the throwout bearing is doing any 'work'. You are correct in that the usual noise that a bad throwout bearing makes is a high pitched squealing. This is because the bearings inside of it are worn/dry, and pressure of being pushed against the pressure plate/clutch dish assembly causes it to squeal.

I have personally experienced worn throwout bearings on my '90 325is and '97 M3/4. I had the slight knocking sound on the 325is and to a lesser extent on my '90 M3. Replacing the entire clutch assembly and the throwout bearing on the 325is did not change the knocking sound at all.

To the original poster once again: changing the transmission fluid is the only thing you can do to attempt to quiet this down. Then again, with 400k miles, a replacement tranny would probably be your best bet!

**joshh** · 09-21-2005, 03:36 PM

I'm going to have leave this at a disagreement. 2 of us are saying the exact opposite of what your saying. I have never had a bearing make noise unless my foot was off the clutch pedal.
The bearing is on the shaft therefor it does spin with the motor and has no load on it till the clutch is used then it does not make noise because the load is on it.

**Brew** · 09-21-2005, 04:20 PM

Originally posted by joshh

I'm going to have leave this at a disagreement. 2 of us are saying the exact opposite of what your saying. I have never had a bearing make noise unless my foot was off the clutch pedal.
The bearing is on the shaft therefor it does spin with the motor and has no load on it till the clutch is used then it does not make noise because the load is on it.

Are you thinking of the pilot bearing? The throwout bearing does NOT spin with the motor, it rides on a sleeve that surrounds the transmission input shaft. And, in general, bearings make noise when they are loaded.

**Eric Giles** · 09-21-2005, 05:09 PM

Originally posted by joshh

I'm going to have leave this at a disagreement. 2 of us are saying the exact opposite of what your saying. I have never had a bearing make noise unless my foot was off the clutch pedal.
The bearing is on the shaft therefor it does spin with the motor and has no load on it till the clutch is used then it does not make noise because the load is on it.

No, read it again-Brew and I are in agreement of what is going on. You are the one that is saying the exact opposite of what we are saying. I honestly hope I am not coming off like an ass, so please forgive me if it seems that way to you. It just seems like you do not fully understand how the complete clutch mechanism works. Although I have only personally replaced one clutch before (not fun on jackstands, I tell you!) I was able to see firsthand how every part works in relation to the others. And I can assure you-when the clutch pedal is not being pushed, the throwout bearing is not moving at all-no spinning, no forward movement-it just sits there in a slot on the release fork.

So anyway, I keep on because I want the original poster to know what is happening to his car. Plus, I want to make sure there is correct information on this board since others use this as a research tool for their issues.

**joshh** · 09-21-2005, 05:15 PM

Edit: Yes it is the pilot bearing I am talking about....sorry about that. But that is the bearing that can make noise.
I would have to disagree again about bearings making more noise when they are loaded. When a bearing is loaded any "slop" or wear is closed up.
It's dry in that area and the bearing makes noise because it's lacking any lube and the bearing doesn't always go the same speed as the shaft.
As soon as you apply the clutch it stops the squeel. Thats what I have experiance with on several cars.

**Eric Giles** · 09-21-2005, 05:28 PM

Originally posted by joshh

I'm talking about the throw out bearing pictured here as #4. http://www.realoem.com/bmw/showparts...g=21&fg=05
I would have to disagree again about bearings making more noise when they are loaded. When a bearing is loaded any "slop" or wear is closed up.
The throw out bearing sits on the shaft and as long as the shaft is spinning the bearing spins as well. It's dry in that area and the bearing makes noise because it's lacking any lube and the casing doesn't always go the same speed as the shaft.
As soon as you apply the clutch it stops the squeel. Thats what I have experiance with on several cars.

Yep, that is the part I am talking about also. Ok, now about bearings making noise. Let's say you have a bad left front wheel bearing. You are going straight down the road and it is not making any noise. As soon as you turn to the right, the weight transfers to the left side of the car, in effect loading the left front wheel bearing. Guess what happens? Yep, that bearing starts making noise. This is the way you determine what wheel bearing is bad-it will ALWAYS make noise when a load is applied to it.

The same thing happens with the throwout bearing. Also note-the only part of the throwout bearing that actually spins is at the very front of the bearing. The inside of a BMW throwout bearing that sits over the input shaft of the transmission has no bearing whatsoever inside that opening. The bearing is located in the flat front of the assembly, which you can see in the diagram you posted. That small flat part of that circle is all that spins-that is the part that makes contact with the spinning pressure plate/clutch disc. The rest of the throwout bearing remains entirely stationary.

Why you have had different results I have no idea-were these BMW's? That might possibly be the difference.

**joshh** · 09-21-2005, 05:32 PM

I edited my post. Its the pilot bearing.

The wheel bearing always has load on it. By turning your changing the load, thats why it makes noise.

None of the cars were BMW's.

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