Alacris

Well, I got my car back from the dealership yesterday. The official repair was "Reverse Idler Assembly" and came directly off a TSB for the rattling.

It made the sound a bit quieter, but it's still there.

Dealership mentioned I probably need a new clutch and/or flywheel. The service manager said, they can open up the transmission and look at the TOB and gears, but if the problem is a worn clutch or flywheel, the bill is on me and I should probably have one handy so they can install it while they are in there. His reasoning makes sense, but it's a damned if you do, damned if you don't scenario.

So I was playing around with this noise and noticed a few things:

1. Rattle exists all the time.
2. It is worse when:
   • The car is warmed up
   • The AC is on
3. When I push in the clutch, the noise only goes away after the clutch is completely disengaged.
4. When I release the clutch, the noise reappears at the point when the clutch engages the flywheel.

So some thoughts on this:
It appears the rattle is dependent on whether or not the clutch is touching the flywheel, not load on the throw-out bearing (TOB).

If it was the TOB, shouldn't the noise abate the instant any pressure is applied to the clutch pedal?

I'm also pretty sure it is not the flywheel bolts being loose. If it was, the flywheel would rattle when the clutch was not engaged and would be quiet when the clutch was in contact. This is the exact opposite, not to mention the obvious engine balance problems from a loose flywheel.

Just throwing some ideas out there. I'm trying to wrap my brain around this before I dump $1k+ in a new clutch.

AC

JasonS

iTrader: (1)

I've got the same problem. Just took mine in this morning, and after 30 minutes, got a call from the dealer that the noise is "normal". I told him there's no way that it's normal, it sounds like a hammer tapping on the underside of the car. Same occurences as yours, though.
I'm going to ask him about the TSB and see what he says.

wingless

iTrader: (15)

I think TOBs suck a$$. Mine has sounded like a rock crusher since it was new.

Is there an aftermarket/ uprated TOB availible?

I'd hate to put a 1500$ clutch in with the same OEM crappy TOB.

bigjhoney

iTrader: (12)

ive got the same problem, i cant stand putting the ac on cause its so loud when its on... I read a couple threads like this over a few months, and alot of people are having the same problem.

Assassin

iTrader: (4)

Yup I have the same problem as well as my friend. Looks like they all make that rattling noise.

go_evo_go

iTrader: (1)

I have an 03 making the same noise. I thought that it was the exhaust rattling against the transfer case maybe? If that sounds stupid Im no mechanic. But it does get quieter when the car is warmed up. It had never happened but I am starting to get some grinding in fourth when driving hard. Is a new cluch going to fix it? Any second opinions? Anyways I hope that something can fix it.

03EvoVIII

iTrader: (4)

Took mine in for that last week with the DPSM there and he authorized a tranny tear down and thinks the the input or output shaft is shimmed wrong and that the extra load of the A/C throws it more out of balance thn it already is with no a/c on... I go in next week so we'll see what happens

Alacris

well, I've spent a good deal of my lunch break going over the service manual and "how clutches work" to see if I can figure out what might be wrong.

First off, nomenclature: it's a release bearing, not a throwout bearing, according to the service manual. They are almost the same thing (one is for push type clutches, the other for pull), as they transmit the clutch pedal force to the pressure plate assembly to disengage it. I only bring this up in case you all try to talk to the service guys -- they can search on the "official" part name.

Anyway, when the clutch is engaged, regardless of in gear or neutral, the release bearing (RB) is away from the pressure plate springs and has the transmission shaft rotating inside of it. This bearing unit has two types of bearings: rotating for the transmission shaft and thrust for pushing on the release springs in the pressure plate. It has a firm mechanical linkage with the clutch fork, so any rattling of the RB should be directly transmitted to the fork. I'm going to try to use an automotive stethoscope to hear if that's where the noise is loudest.

If it was the RB rattling, any force applied to it should shut it up. Similar to when you find the rattle on the dash. When you put your hand on it, it stops. But this rattle doesn't go away immediately, it only disappears when the clutch is fully disengaged. It also reappears as soon as the clutch is reengaged.

This leads me to believe that it's a problem with the input shaft in the transmission. When it "freewheels" under no load it rattles, when it has a load (in gear), it's fine. I'm going to try a few experiments tonight on my drive home and see if I can get it to rattle in gear at low rpms. I'm betting I can't, but thankfully traffic on the way back gives me plenty of opportunities to test the car at low RPMs

Alacris

Okay, no stethoscope last night, but I did try an experiment:

Car on level ground, in first gear. Slowly let out the clutch without applying any gas.

If the release bearing was rattling, it should rattle with the car in gear the moment it stops contancting the pressure plate springs (the theory being we just don't hear it over the transmission/engine noise). Well I kept everything very quiet and no transmission rattle when the car is in gear.

So input shaft it is. This may indeed be a normal noise. It doesn't appear to affect drivability, but as for any metal-on-metal noise, I'm worried about accelerated wear or worse, catastrophic failure at some point.

But I'm no automotive expert, just a curious engineer with a service manual and an internet connection

Any thoughts on this?