Any ideas ... troubleshooting a clickety clunk
 

While driving suddenly developed a new onset cyclical click (or is it a clunk? ... somewhere in between, a hard metallic version of a a baseball card in a bicycle wheel) yesterday. Car drives fine, no vibrations. Hard to discern a location, but more mid/rear not front.

Only occurs when in gear. Increases with speed (rpms?). Seems to sound worst between 2000 - 3000 rpm. When the clutch is engaged or the car is put in neutral the sound DISAPPEARS, even while in motion. The sound does not occur at idle or when i rev engine at idle.

The sound was there for an hour at very low speeds (creeping with no accelerator in 1st gear) and at higher roadway speeds. Then it seemed to go away for an hour. I was pleased. Then it returned for 1/2 hours.

Any ideas?

Does it sound like marbles in an empty coffee can?
If so, don't drive it - have it towed to a Porsche mechanic or dealer.
That is the indication that the IMS is about to go. When the IMS goes, it can cause "catastrophic" engine failure.
Read up on IMS on this forum and at: http://www.lnengineering.com/ims.html

IMO, the IMS would make the sound in neutral since it would still be spinning, then again it would be worse under a load for shizzle.

The brake cable is tied back and if the tie breaks, it could come in contact with the wheel. Check the back side and see if it's hitting. :cheers:

While you're there, look for any scoring on the discs where anything could be intermittently hanging up,check the CV joint too.

and check the axle shafts

And the mounting flanges on both sides.

quick update ... it seems pretty intermittent ... there was no sound at all this morning (cold start followed by 10 min drive).

all very good ideas, but sure about the interaction of these noises with the clutch (eg why would a loose brake cable sound go away when I engaged the clutch?). Pretty sure its not IMS ... sound is way too slow when I am creeping along (like one click every 2 or 3 seconds). And its just not there at all at idle. My first initial impression (which might be quite wrong, I was in the drivers seat) was that the sound was coming from the right rear wheel well.

Was wondering about the tranny mount??? ... otherwise can't figure out what that could be if engaging the clutch (or coasting in neutral) takes the sound away?

look to see if the bolts are loose on the axle

I say DMF - Dual Mass Flywheel. It could be worse.

Cheers!

when you hear the sound, does the frequency increase / decrease with engine speed (RPM), or with vehicle speed (MPH)?

and what model / year / trans?

The frequency increases with vehicle speed (not RPMs). So if 'no noise when depressing clutch' means trans not engine, then 'varies with speed not rpm' means ? i'm wondering about axle to cv joint?

Sounds like something is knocking, but its difficult for me to describe well.

Its a 2001S with a 6 speed manual

you mentioned that it stops when you're out of gear or when the clutch is pressed. what about when you vary load? does it go away when you get on the gas? when you let off? how about in corners; does it go away? get worse?

Nope, does not seem to change with gas (nor brake), nor around corners (although it was harder for me to assess the latter on my short drive to work today). My newest description for the sound today is like a cracking sound.

what's the approximate frequency if you had to guess? 60 beats / minute? 120? trying to figure out if it's like a buzzzzzz or like a crack crack crack

also, are you CERTAIN it's coming from the right side, or is it very hard to tell which side it's coming from?

I stuck my phone out the drivers side between red lights and recorded 30 seconds, rather than continue to describe it badly. I think the car was generally between 2000 and 3500 RPM in this 30 sec stretch. The sound stops abruptly at the end because I engaged the clutch and coast the last little bit.

Its definitely a crack, crack, crack.

I haven't had assistance from anyone, and its only audible when driving, so all I can tell you is from the perspective of the drivers seat. To me it sounds like right rear, but it could be coming from absolutely anywhere.

http://audioboo.fm/boos/179980-boxster-2001s-noise

As you will hear, the frequency varies with the speed of the vehicle. I do think there are times when I have been able to rev the car out of the noise (it seems a bit less distinct above 3000 RPMs, and its felt at times that I rev out of it around 4-5000 RPM. I felt like when the car lurched the sound would start up again. That could all be in my head though. I wondered if there were a few times I didn't rev out of it -- hard to tell because the engine sound drowns out the click around that level, and it would 'return' around the same time it would have become audible regardless)

Thanks for all advice offered. Its raining now, but I need to figure out what to look for / how to look at it and get under her this weekend.

i can't be sure without driving the car, but my gut tells me that the ring gear in your differential is damaged. a seasoned porsche mechanic should be able to drive it a hundred feet and tell you if that's the cause of the noise.

(i hope i am wrong!)

have you ever had the transmission fluid replaced? if it was filled incorrectly, this can happen.

lol diagnosis via Internet. :)

no, but i just bought the car a month ago.

what makes you think it is the ring gear in the differential?

other than inspect cv joints (is there a way that depressing the clutch could remove cvj noise????), is there anything else i can / should do to inspect for the obvious?

what would a porsche vet be looking for when driving the car that would be indicative?

the CV axles would generally make noise all the time, and the noise would have a higher frequency & a different sound. pressing the clutch would not affect CV noise.

other driveline issues could be the flywheel, clutch, throwout bearing, etc, but all of these would vary with RPM, not with vehicle speed.

the pinion gear & ring gear in the diff would both vary frequency w/ vehicle speed. when the pinion is damaged, the sound frequency is high, more like a freewheeling 10-speed bike. when the ring gear is damaged, the sound is very similar to what you recorded. also, relieving load from the gears by pressing the clutch or hitting neutral CAN make the sound go away. it will, however, get worse over time, and will eventually happen whenever the car is in motion.

i would still have a seasoned porsche tech drive the car & give you his impressions; i could certainly be wrong. it's hard to diagnose car noises over the internet.

FYI, a ring gear isn't all that expensive, but it can be tricky to install properly. the real issue is (if this is the transmission) that the pinion could be damaged, too. this is DEEP in the tranny & hard to replace. if this is indeed your problem, the easiest solution is to source a tranny from a wrecked car & install something else.

another thing i recommend? take someone for a ride and ask them which side the noise is on. i bet they say the left. if the driver hears it left & the passenger hears it right, it's in the center......transmission.

let us know what you find out.