Chatter under load, between 2k and 3500 rpm

[shiftbmw]

Alright, I asked this on s14 but I figure I'll get a different set of opinions.

I'm experiencing an obscene chatter between 2k and 3500 rpm. It's audible with the windows closed and open, independent of motor temp, and has not gotten any worse with 1000 miles of driving on it. The car must be in gear to hear it(can't hear it when I rev out of gear). I've gotten under my car and pretty much tapped everything with a hammer to no avail. From the drivers seat, it sounds like it's coming from the passenger side of the car, towards the bottom.

*update* I think it actually gets quieter once the car is warm(I'm talking once the oild gets warm after 10 minutes of driving).

I've hit all the underbody heat shields, including the cat, my header bolts and exhaust tranny bracket are tight, a/c compressor bracket tabs are fine...and the list goes on. It doesn't exhibit symptoms I'd associate with timing chain chatter...but you never know.

Car is an 88 m3. Any of you guys have an opinion or experienced something similar?

[DaN]

Could be driveshaft center support bearing, the rubber centering bushing in the driveshaft at the flex disc, or the flexdisc itself.

[shiftbmw]

It's definately not the guibo. It is a distinctly metal on metal sound.

To clarify, it's not a vibration I can feel...I can only hear it.

What's the best way to check the center support bearing?

[NC325iC]

what does it sound like?
ticking, metal to metal,

[browntown]

does it happen in every gear?

[shiftbmw]

what does it sound like?
ticking, metal to metal,

It is a metal on metal sound...its almost reminiscent of timing chain chatter.

[shiftbmw]

does it happen in every gear?

It happens in every gear, but it's minimal(95% of the time it's completely inaudible) in 1st. It's audible 100% of the time in all other gears.


Correct me if I'm wrong, but a timing chain chatter will reveal itself most when the chain itself is accelerating the hardest because the tensioner "can't keep up." By this logic, if it was chain chatter, I should be able to induce it most easily while reving in neutral because that is when the chain will be accelerating hardest, right?

[b*saint]

Ever think it may have something to do with the clutch? (Throwout bearing or w/e)?

[porsche gt1]

is it a ticking? if so could be your valves out of adjustment. If it is more of a grindy grindy, I would check the entire drivetrain.

[shiftbmw]

is it a ticking? if so could be your valves out of adjustment. If it is more of a grindy grindy, I would check the entire drivetrain.

It's not the valves, the sound doesn't exist unless I'm in gear(you'd hear valves out of gear).

It's a chatter, not a grind. Imagine taking 2 coat hangers and drumrolling on a piece of sheetmetal...

[shiftbmw]

Ever think it may have something to do with the clutch? (Throwout bearing or w/e)?

I have thought that, but my symptoms don't seem to point towards any sort of tranny problem. New fluid in the tranny did nothing to lessen the noise, and to my knowledge, there are no bearings that would act up while in gear between certain rpm's...

[92 mtechnic cabrio]

Might be exhaust related if it's only under load.

Might be a leak somewhere, or might be the cat.

[shiftbmw]

Might be exhaust related if it's only under load.

Might be a leak somewhere, or might be the cat.

I've tagged every heat sheild and braket connected to the exhaust with a hammer and not so much as a rattle...

[Koony]

Sounds to me like a bad CV-joint if it's isolated to one side of the car. Drum rolling sound would lead me to center support bearing, but you should be able to feel the driveshaft thumping around.

[shiftbmw]

Sounds to me like a bad CV-joint if it's isolated to one side of the car. Drum rolling sound would lead me to center support bearing, but you should be able to feel the driveshaft thumping around.

Would a CV-joint only be apparent at certain rpm ranges or would it be constant? Also, would the noise diminish with heat?

I wish I had a better way to describe what it sounded like...rain hitting a tin roof?