Strange Front End Eng/Trns Noise on 06' CTT

[CTTinTO]

Yep, this noise is a strange one.

On a 06' CTT , I've had it for about a month and started to notice this noise a few days into ownership and I am not entirely sure if it is a normal noise or not.

At around 1800-2000rpm under load, during a standing start (normal to medium agressive) I hear a noise from the front for about 1-2seconds. Its difficult to describe but its sound somewhat like an erratic squeal. Like a pulley with a slight belt slip. When it happens which is virtually every time I take off from a standing start, I can also feel it vibrate through the accel pedal fairly well when it happens.

I've thought of it being either

(1) front diff? if its an electronic type diff with clutches it may be a possibility of noisy clutches - I need to do more research in the design of the differentials of the CTT

(2) Diverter Valve? it is my understanding that factory units over time fail but what type (if any) noises do they produce when they are pooched? Engine boost as per gauge seems to be normal but it could have a small leak somewhere that might not be easily noticed on the gauge

(3) Engine Internally/Turbos? who knows... anyone with experience?

Anyhow, just seeing if anyone out there may sound this all familiar...

Edited September 21, 2010 by CTTinTO

[wvicary]

Have you inspected the driveshaft centre brng?

[CTTinTO]

Have you inspected the driveshaft centre brng?

I've done a quick visual on the bearing and it looks to be OK ie: no cracks

The noise also seems to be clearly from the front of the vehicle and can be felt through the accel pedal and steering wheel.

What type of noise does the driveshaft center bearing make when it is on its way out? I've never experienced this phenomena but I would assume that the noise would be more like a failing bearing and increase in noise levels with speed combined with some steering/body vibration.

My particular car drives extremely smooth at hwy speeds and the noise only seems to happen during initial acceleration.

I'm now considering changing the front diff's fluid to see if there is an improvement...

[jsrbrown]

Have you inspected the driveshaft centre brng?

I've done a quick visual on the bearing and it looks to be OK ie: no cracks

The noise also seems to be clearly from the front of the vehicle and can be felt through the accel pedal and steering wheel.

What type of noise does the driveshaft center bearing make when it is on its way out? I've never experienced this phenomena but I would assume that the noise would be more like a failing bearing and increase in noise levels with speed combined with some steering/body vibration.

My particular car drives extremely smooth at hwy speeds and the noise only seems to happen during initial acceleration.

I'm now considering changing the front diff's fluid to see if there is an improvement...

I have this exact same issue. Did you ever fix it or figure out what it was?

[rizzo]

Front differential is probably failing.

[CTTinTO]

noise is still there and hasn't gotten any worse so I've learned to live with it. Its really not that loud except now that I've "tuned" into it, I can hear it every time.

I suspect it may be the front diff as well which is why I plan to change the diff oil at my next oil change interval. I also have a friend that works at the local porsche stealer and he is supposedly the resident Cayenne expert. Hopefully in the spring I can get him to take my CTT for a spin and give me his opinion.

[jsrbrown]

Good deal. I'm working on getting the same thing done.

[Reza]

Hello CTTinTO:

Did you figure out what caused the sound?

Let me explain a similar sound I have on my CS04 which is kind of similar:

Whenever I start the engine and start moving from stand still, after about 20 seconds of driving I hear a squeak sound (maybe more like the sound you hear if you pull a spring and release it, or sound of a mechanical pump pushing a fluid into a device with pressure and very very similar to the sound you would hear when ABS pumps start to react when wheels are sliding on icy road).

The sound comes from front, right side, of the vehicle.

(if the weather is too cold and car starts in D1, the sound never comes out until it moves to D2 and then after 3 seconds being in D2 it is heard, so it is like total time of 20 to 30 seconds after engine start and first move, if weather is warm and I start in D2, it is also heard within 10 to 20 seconds of first move). I Won't hear that anymore, even if I stop, park in P gear, then D and move.

If I turn the engine off and ON again and start from stand still, the sound comes back.

Is that Normal? Any help would be highly appreciated.

[CTTinTO]

Hello CTTinTO:

Did you figure out what caused the sound?

Let me explain a similar sound I have on my CS04 which is kind of similar:

Whenever I start the engine and start moving from stand still, after about 20 seconds of driving I hear a squeak sound (maybe more like the sound you hear if you pull a spring and release it, or sound of a mechanical pump pushing a fluid into a device with pressure and very very similar to the sound you would hear when ABS pumps start to react when wheels are sliding on icy road).

The sound comes from front, right side, of the vehicle.

(if the weather is too cold and car starts in D1, the sound never comes out until it moves to D2 and then after 3 seconds being in D2 it is heard, so it is like total time of 20 to 30 seconds after engine start and first move, if weather is warm and I start in D2, it is also heard within 10 to 20 seconds of first move). I Won't hear that anymore, even if I stop, park in P gear, then D and move.

If I turn the engine off and ON again and start from stand still, the sound comes back.

Is that Normal? Any help would be highly appreciated.

sorry Reza but based on your sound description, I don't think your noise is the same as the one I am experiencing.

Btw, went to the dealer on the weekend and picked up the front diff oil - $65 for one litre!!! that is crazy

[wvicary]

Hello CTTinTO:

Did you figure out what caused the sound?

Let me explain a similar sound I have on my CS04 which is kind of similar:

Whenever I start the engine and start moving from stand still, after about 20 seconds of driving I hear a squeak sound (maybe more like the sound you hear if you pull a spring and release it, or sound of a mechanical pump pushing a fluid into a device with pressure and very very similar to the sound you would hear when ABS pumps start to react when wheels are sliding on icy road).

The sound comes from front, right side, of the vehicle.

(if the weather is too cold and car starts in D1, the sound never comes out until it moves to D2 and then after 3 seconds being in D2 it is heard, so it is like total time of 20 to 30 seconds after engine start and first move, if weather is warm and I start in D2, it is also heard within 10 to 20 seconds of first move). I Won't hear that anymore, even if I stop, park in P gear, then D and move.

If I turn the engine off and ON again and start from stand still, the sound comes back.

Is that Normal? Any help would be highly appreciated.

Even though you are hearing the sound from the right front I would think you have a problems with the centre brng in the carden shaft. I have heard a very similar noise shortly before the shaft failed.

[Reza]

Thanks for the replies.

I have had this sound coming after every first start and move from stand still since October 2010... I wish to know what it is? could that be related to brake booster pumps because as I said it is very very similar to the ABS Pumps when they operate on a slippery road.

[Reza]

I let dealer check on this and it appeared to be normal. It is in fact the ABS pump pre charge that is done after every start up to make it ready for ABS operation when needed.