MountainStone

Took my new-to-me 2011 CTT to the only dealer in town today. When pulling away from a stop, accelerating through a left turn it makes a 'crunch' sound and concurrent vibration from the rear end. Sound isn't terribly loud but it's there, and the momentary vibration draws your attention to it. The service manager drove it and was able to replicate it. I pointed out that it seems to coincide with the upshift to 2nd gear. They gave me a loaner and said they will attempt to diagnose, but the service manager told me he's been in other cars that displayed identical symptoms and he was pretty sure it was normal. This is my first Porsche; is this normal behavior? I have the sport package, so I dunno if having PTV+ is a factor.

pastorom

Not to speak to the 'normalcy' here, but this is *exactly* what i've been noticing on my new to me 2011 CTT too. Only happens when i start off from traffic lights and stop signs. Only seems to happens when the start involves a turn, so i'm i'm just going straight it doesn't seem to happen.

I've owned a 2004 CTT before, and it didn't seem to do this, but then again, the 2011 CTT has PTV+, PDCC etc, so unsure if the newer tech is responsible for this.

It's funny, i was debating on posting about this topic as well, but held off because i wanted to try get audio confirmation. Sub'd - will be interesting to hear responses.

Dalema

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Petza914

Sometimes if a rotor is slightly warped or a wheel bearing is worn, the loads associated with a slight turn can result in a little bot of brake pad contact that can sound like a scraping sound, but I wouldn't compare this sound to the loud clunk that happens in the cold at full lock in a 997 due to the suspension geometry.

Interested to see what the dealer comes back with.

CarGuyNVA

Ding Ding Ding!!! Yes, funny you all should mention this. My 2011 CTT with PTV+ exhibits the exact same symptom. It is normal, and is a trait of the electronic locking differential that's a key part of the PTV+ option. It doesn't happen in every case (slow rather tight left turn), but happens quite often.

I've had other non-P cars with limited slip differentials (LSD) that exhibits the same symptoms. In those vehicles it was the LSD clutch packs in tight slow speed turns that would cause them to 'rub' a bit and cause that same result. Perfectly normal in those instances. Basically the same thing with the PTV+ setup in our CTTs.

termite01

This thread made my day! My 2011 CTT with PTV+ does the exact same thing and driving over acorns is a perfect description for slow speed left turns. It is worse when cold but I can duplicate it on demand...

marylandmark

Same here. 2011 CTT with PTV+, PDCC, etc. I just thought it was my mix of Summer tires in the rear and All Seasons in the front.

Thanks for answering!!

rloggie

Mine sounded the same, especially when cold. Dealer found that the rear differential was bad and replaced it for 4,300, under fidelity warranty. 2011 CTT, 26Kmi

termite01

Mine was first diagnosed as a failing transfer case by the dealer that sold me the car. They put in a brand new transfer case and it still does the same thing...is it possible that all of the posters above with 2011CTT's have shot diffs? if everyone could list their mileage it would help. Mine has 32k miles with both PTV+ and PDCC.

marylandmark

68k miles on mine but I've only owned it for 5k miles. I bought this one:

https://rennlist.com/forums/vehicle-...e-country.html

ETA:
WD311 re-program RA rear diff lock 9/17/14 at 34k miles
WC261 re-program re-program all wheel drive control unit 9/17/12 at 11.5k miles
​​

pastorom

90k on mine. Had PPI done by dealer before purchase, and passed with flying colors. Which means very little, but they explicitly list 6 line items for differential checks, and mine seems to have passed all of them.

Dalema

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CarGuyNVA

I don't think that's possible to disable the PTV.

Again, I don't think the noise indicates a problem/malfunction. I believe it's a trait of the locking diff, similar to what you sometimes experience in other vehicles with limited slip or locking diffs. If you notice it doesn't do it at 'normal' driving speeds, only very slow speeds moving from a stop with the steering wheel turned to the left. Same as I've experienced with other LSD equipped vehicles I've owned. Plus everyone here with PTV seems to be reporting the same experience.

garrett376

It's the transfer case and/or the rear PTV differential. Replacing both is often necessary.
Applicable tech documents: advanced technical information number 3965 regarding the transfer case, and WM 390155 Eliminating transmission symptoms regarding the rear differential.

So it is a problem/malfunction enough that warrants replacement (if you're covered), which cures this issue completely.

garrett376

You can unplug the transfer case so it's disabled, and drive it and the thumping will stop if it is solely the transfer case (most noticeable on a slight uphill with a slight left curve under low throttle from a stop). From a wear standpoint, it's probably going to take replacing both to get it to go away.