getfast
getfast New Reader
12/14/10 11:24 a.m.

Hey guys, I'm trying to figure out a weird noise that my beater '95 325i is making, please help.

I have not heard this particular noise before on any of the dozens of E30/E36 cars I've been around over the years, it's been doing it for at least a thousand miles now and it's not getting any quieter.

It's definitely a whirrrr or whine (not a rattle), it sounds kinda like a supercharger or the start of a bad power steering pump.

It whines the worst when the engine is idling and the clutch pedal is pushed to the floor and the car is not moving, whether it's in gear or not.

Conversely the whine is most quiet when the engine is idling and the clutch is disengaged and the car is not in gear and not moving.

Then it makes the whine when the clutch is used and during acceleration through the lower part of the rev range, especially in 1st and 2nd. Reach a certain rpm - like somewhere around 2500 - and the noise goes away. At highway speeds/revs I can't hear it at all.

There is no vibration and no clunking going into any gears, the clutch slips a bit (but doesn't chatter) and the car shifts fine otherwise (but does have the usual sloppy shifter.)

Its pitch changes with engine speed, not wheel speed (ruling out a diff or driveshaft issue?)

Bimmerforums suggests transmission input shaft bearing, but isn't the input shaft not spinning when the clutch is engaged and the car is not in gear and not moving (i.e. when the noise is the loudest?)

Doesn't a bad release bearing just chatter/rattle, not whine (and only make noise when it's disengaged)? How about a bad pilot bearing, could that be the culprit?

I'm mostly curious because the car is getting a new clutch soon, and I'm in the assembling-of-parts stage now. I'd like to do the job once and forget about it.

Many thanks for your thoughts,

Jon (ps- I may be able to post some video later today if the above description is unclear)

93celicaGT2
93celicaGT2 SuperDork
12/14/10 11:25 a.m.

I'm actually with Bimmerforums on this one, but i'm no expert.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
12/14/10 11:30 a.m.

Input shaft bearing it is.

Check the fluid in your gearbox - the way this usually happens is that either the front or rear seal leaks and eventually the level in the gearbox leaves the front bearing dry (its the highest point compared to the sump).

tuna55
tuna55 Dork
12/14/10 11:34 a.m.

Sounds like a transmission bearing. It only makes it at low speeds because that's when you're really imparting a side load on the gears themselves. In fourth or fifth just cruising I'll bet it's silent. Check the fluid, but it's probably shot. Bearings are really cheap, though, for just about any manual tranny. Putting them in, however, is not trivial.

getfast
getfast New Reader
12/14/10 11:41 a.m.

Thanks guys! That's exactly what I was hoping to avoid - having to take the gearbox apart to deal with this bearing.

There's enough fluid splatter underneath that I can't really tell what's what. The car has a semi-unknown history, for all I know the trans fluid has 139k miles on it now.

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
12/14/10 11:51 a.m.
getfast wrote: It whines the worst when the engine is idling and the clutch pedal is pushed to the floor and the car is not moving, whether it's in gear or not.

DOH. I should have read that a little closer. Yeah. The input shaft won't be turning with the car in gear and the clutch depressed. I somehow read it as "loudest in neutral with the clutch released".

It could just be the TO bearing - they usually rattle but they do have a roller bearing in the face against the clutch fingers.

getfast
getfast New Reader
12/14/10 2:16 p.m.

Thanks for the clarification. Sure hoping it's that and not something inside the transmission - not trying to spend any more money than is absolutely necessary, also trying to knock out the clutch job in half a day or less

That said... release bearing, pilot bearing, pivot pin, spring clip, seals, etc are all getting replaced during the clutch job. Sure I could find a good used trans for a few hundred bucks but see above, this is a beater.

tuna55
tuna55 Dork
12/14/10 2:48 p.m.
Giant Purple Snorklewacker wrote:
getfast wrote: It whines the worst when the engine is idling and the clutch pedal is pushed to the floor and the car is not moving, whether it's in gear or not.

DOH. I should have read that a little closer. Yeah. The input shaft won't be turning with the car in gear and the clutch depressed. I somehow read it as "loudest in neutral with the clutch released".

It could just be the TO bearing - they usually rattle but they do have a roller bearing in the face against the clutch fingers.

Yup - didn't catch that either.

getfast
getfast New Reader
12/14/10 10:56 p.m.

Well the good news is that a local E36 guru thinks it's "definitely clutch related, not internal " after a test-drive.

The bad news is that the $100 old-but-new-in-box clutch kit I went to get from a buddy turned out to be for an E30.

7pilot
7pilot Reader
12/15/10 7:46 a.m.

Hearing the noise when you depress the clutch pedal....Clutch release bearing. It starts as a whirr, gets louder, then you start to feel the fine vibration in the clutch pedal when it is depressed the the ambient temps lower.

m

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