KrisKringle

So, yesterday I hear this metallic noise coming from just aft of driver seat.
Sounds like a short 'clang' of a light metal and is not very loud at all. (sorry best description)

Happened when I eased of the gas in 3rd gear and than added a bit. Only around 2000-2300rpm.

Could recreate it by letting off the throttle to 2000rpm and giving light throttle input. Only audible for a fraction of a second as the light throttle is applied.

Can do the same in 4th gear.

Car picks up normally otherwise and clutch pedal feels normal.
More abrupt throttle input does not recreate the effect.

2003 C4S with about 40k on it.

Is this the clutch or possible issue with the AWD? Input welcomed.

Pac996

Any chance of recording audio?
I'd even wonder if its possible a line hidden by the bottom cover plates is not secured in place.
At first it seemed you were describing what could be a vibration oriented metal to metal contact since you say it is during light torque periods.

Shark Attack

IMS clanking in the worn out bearing.... J/k (I hope)

KrisKringle

I'll see what I can do audio wise Will try tomorrow.

I don't think it's a loose object/line as I don't hear it when driving over a bump.

Metal to metal is accurate (lets say similar to a light metal object tapping a sheet of aluminum).

Pac996

I know when my sister road in the car and said, 'what's that sound' I first listened then told her to cut it out after she said she doesn't hear it anymore. Some times we are sensitive hearing everything and other times we go straight to saying shut up.

Van

You know, some of the bearings in the transmission are of the same "sealed" variety as the IMS bearing. They don't get any external lubrication - and will sometimes fail.

If I had to guess - if you're really hearing a metalic interface kind of noise - I'd say one of these bearings has eaten it's self.

KrisKringle

with a failed bearing, would the noise not be there at wider ranges and/or more often?

Any other trouble shooting ideas?

fbgh2o

Yes, you will hear elevated transmission noise under load if the pinion bearing is going and just generally a load transmission if the main shaft bearing is going. I am getting my transmission replaced for those reasons exactly. Although, I have never had a metallic noise like you are describing, just whine from friction.

goliver

The Pinion bearing went south in my tranny and it was a whine under load. Got louder and louder over time. When my water pump let loose, it made a chirping sound at first and then a minor metallic clunking very faint. Maybe that is the sound you are hearing.

KrisKringle

tried recording it, but no joy, too faint for the microphone to pick up.

No noise at higher rpm, just the brief clang. Will get local indy to come for a drive to see if we can figure this out.

cbzzoom

Hey, bumping old thread because I have this *exact* problem in my 2006 C4S with 40k miles. Yeah I know it's a 997 and I'm in the wrong forum, but I've never seen these exact symptoms described before.

I've had the car into the dealer, but of course it refuses to make a good clunk when a tech is sitting in the passenger seat

OP, did you ever find anything out about this?

I'm trying to narrow down exactly what could be causing it. Some more information :

1. It's a "clunk" or a bit of dull clang; it sounds like it's coming from the drivetrain somewhere. It only happens when you get on the throttle gently around 2k RPM, it'll clunk and then the RPM picks up. Once you are up in higher RPM you can feather the throttle all you want and it won't clunk.

2. It seems to happen mostly if you are coasting (eg. giving no throttle and the car is slowly deccelerating) and then get on the throttle lightly, thus reversing the flow of torque through the driveline. Might happen more when coasting up hill, but can't say that for sure.

3. Happens mainly in 2nd or 3rd. I think it's easier to repro in 3rd. Probably happens in all gears, these are just the easiest ones to coast at 2k RPM.

4. It almost never happens when the car is cold, and it's much louder once the car is well warmed up after a few hours of spirited driving. Seems to indicate something about the lube getting warm.

5. Never clunks going over bumps or turning, only on throttle application, so I don't think it's any kind of loose piece clanging. Also had the motor mounts inspected so that's probably not it either.

There are a few things that are odd about it : there's no clunk when coming to a stop or when starting from a stop; those would be standard hallmarks for driveline lash. There's no clunk when changing gears, that would be a classic symptom of a DMF failure.

My best guesses are something in the AWD or the DMF. It's when the driveline is loaded in reverse (coasting up a hill) and then you get on the throttle, but only at 2-3k RPM, not higher, which is weird. Maybe it's a specific resonance.

I'm sure I could ignore it and the car would be fine, but it's driving me a bit batty. I'll see if I can get an audio recording.

eggodynamics

Definitely sounds like a faulty turbo encabulator.

http://www.youtube.com/watch?v=rLDgQg6bq7o

Dave!

Maybe the flywheel? I can imagine the springs dying and when the rotational load flips there'd be a bit of lash as the dual mass clanged together.

This is 100% guesswork though.

Maybe it could also be a driveshaft wearing out--they get a good bit of rotational free-play as they go.

Again. Guesswork.

Edit: You can check the driveshaft though, put it in gear and set the parking brake the grab the shaft and try to move it around. If there's any play in the shaft (moving around or rotating) the shaft is going bad.

cbzzoom

I went out driving for a few hours on the weekend hoping to make the clunk happen and get a video of it - of course no clunks at all ; so then driving home from work today I've totally forgotten about it and then blammo - clunk, so I whip out my camera and try to get a recording real quick - quality's not awesome, but you can definitely hear it :

http://www.youtube.com/watch?v=phrzPy90XwM

you can see it only occurs right when you get on the throttle at 2k RPM. If I pulse the throttle at 3k RPM, no clunk. It's weird to me how it has to be right there.

Graufuchs

Back on topic....that almost sounds like my old 944 when the rubber puck started to come apart and it would clunk when beginning to accelerate...