MountainStone

Wow. Surprised to hear that six other owners experience the same symptoms. I've owned other cars/trucks with LSDs and own a truck with a locker and have never heard/felt this sound. Even if it's common it can't be harmless, can it? Something is vibrating pretty significantly under there. BTW, mine has 55k miles.

Anyway an update: my SA called to say the tech can reproduce the sound at will but they drove another Cayenne and it DIDN'T make any noise so they decided it is not normal. They put it on the rack but could not determine the source, despite using a pry bar to exercise all of the suspension. He requested authorization for additional diagnostic time, stating they intend to mount an electronic sensor to various components while driving the car reproducing the sound. They wish to pinpoint the source before opening the offending component (diff, transfer case, transmission, etc.). If they find a failed component, Fidelity will pay the bill. If they ultimately determine it really is normal, I foot the bill for however many hours of diagnostic time they spend. I'm actually not sure what to hope for. Maybe I'll call to mention six other owners all report identical operation and request he check a Cayenne with PTV+.

I'll update again tomorrow; stay tuned.

garrett376

Just have them look into those references I've listed above. Any dealer can access those.

MountainStone

Thanks Garrett (you posted while I was replying). Can I tell the SA to reference those two documents and he will know what I am talking about?

Do you know whether these symptoms lead to failure of one or both of the components?

Again, thanks for weighing in!
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CarGuyNVA

Interesting information here. I'll check my vehicle's service records this evening, but I know the transfer case was replaced at about 35k miles and there are a couple of records for campaigns completed on my CTT involving the rear locking diff. It may be what's referenced above. If it is/was, mine still makes the noise and has since I've owned it (6 mons.) I'm at 59k miles currently.

I'll be interested to hear what the OP's dealer says about his following the diagnosis.

CarGuyNVA

So we're not the only ones that have noticed this before. Check out this thread below from another forum from 2012. Lots of additional information here.

What I gather from this thread below is it seems either a new differential or more frequent diff fluid changes with the proper lubricant seems to address it, and it is definitely PTV related. As for the diff replacement though, I noticed one person says they had their diff replaced and it was quiet for a time, but then the noise returned. Same with folks that did the fluid change. So maybe the thing to do is stepped up fluid changes according to what I'm reading here? Even a diff replacement doesn't seem to be a sure thing. There's also some software campaigns/updates for the rear diff on PTV equipped vehicles that appear to minimize it. All of this shows that Porsche is aware of it and has made some attempts to minimize it, but it seems the noise to some degree is a 'normal' trait of the PTV system on these vehicles?

Again as I mentioned in my post before this one, I know my service records show some campaigns having been performed related to the rear diff on my CTT. I'll check tonight but I believe they're the ones mentioned in this informative thread.....

http://www.6speedonline.com/forums/c...nne-turbo.html

pastorom

Thanks for the info! I can confirm from my service history, that i see WC-26 and WD-31 both performed on my car (Reprogram Rear Diff Lock Control Unit). This seems to line up with what you suggested. Both of these were performed around 37k on my car.

I also see at 82.5k, a service record that states "customer complains about 'grinding' sound". A 4 wheel alignment was done, which seems to have mitigated this.

So, a combination of fluid changes, software changes, and alignments?

CarGuyNVA

Yep, that's what it seems to me based on what I've read of others experiences.

And those two campaign codes you mention above related to 'Reprogram Rear Diff Lock Control Unit', I think those are exactly the ones that have been applied to mine too, but again I'll double check my paperwork tonight.

So next time mine's at the dealer for an oil change, I'll probably just ask them to replace the rear diff fluid also.

Still interested to hear what MountainStone's dealer comes back with as well.

CarGuyNVA

Okay, I checked the dealer service records for my CTT and mine has had it all done....the ATI 3965 for transfer case replacement, the WC26 for 'recall - reprogrammed 4 wheel drive', and the WD-31 'reprogrammed rear diff control unit'.

And just like other owners in the thread from another forum I provided a link to earlier today, mine still makes the noise occasionally on slow tight left turns. It seems that more frequent rear diff fluid changes with the approved fluid keeps the symptom mostly under control, again as mentioned in the other thread. Even those that had their rear diffs completely replaced, the noise eventually returned (probably as the fluid aged?). It makes sense to me because as I've mentioned before, other vehicles I've owned with LSD/locking diff units have sometimes exhibited a similar condition which was often tamed with a fluid change using the correct fluid with the additive to specifically quiet and smooth operation of the LSD clutch packs. These additives do wear out. Something very similar going on here with the PTV setup I believe. Nature of the beast? I'll just have my dealer change the rear diff fluid next time I go in for an oil change.

Even with this quirky trait of PTV, I'd still opt for it again. Combined with the PDCC, it makes for a great handling SUV.

MountainStone

UPDATE: The dealer doesn't know what is wrong.

Despite yesterday telling me they could produce the symptom at will, today my SA says they cannot produce it consistently enough to pinpoint the source. I provided the information from Garrett above, but they said they reviewed that first and it changed nothing. Fidelity will not authorize a search of components, so unless I wish to pay for them to start replacing components, I am stuck with this sound. The SA did offer the helpful advice that hopefully a component will break and make it obvious enough that their service department can actually diagnose the issue.

I asked what I will owe when I retrieve the car tomorrow, and my SA reminded me I authorized 4 hours of diagnostic time totaling $600 plus tax. I asked him for my $600 diagnosis and he paused and said he would talk to the Service Manager to probably get it reduced. I'll update again tomorrow with the price Gaudin Porsche in Las Vegas charges for a shrug. I'm guessing it'll be pretty outrageous based on the absence of pride/shame and the prices they quoted for items found during the 'World Class Inspection':
Wiper Blade replacement - $177
Washer nozzle replacement - $61
Front Brakes - $1775
Rear Brakes - $1188
Oil Change - $295

Doug_B_928

I like how you phrased that..."What's my $600 diagnosis?" I also literally LOL at the $177 for wiper blade replacement.

MountainStone

I found the washer nozzle for less than $8. I guess the owner needs the extra markup to pay for the 911R he just bought himself. To go with the 918 he also has. I suppose he's the type of customer that would pay $177 for a $40 pair of wipers.

GDA

Have you checked the simple items like front / rear strut mounts? Those make crunching like noises if the mount has broken through its rubber bushing and can cause all kinds of weird lower and higher speed vibrations that sometimes mimic a early bad wheel bearing.

MountainStone

Yes, the service techs put it up on a rack and used a pry bar to exercise all of the suspension components. They found nothing amiss.

termite01

My saga has turned toward the twilight zone. My 2011 CTT with PTV+ had the same issues and when I bought the truck, the McLaren dealer changed out the transfer case. I still noticed the problem and it was worse when the truck was cold. Following the posts above, I dropped it at the local Porsche dealer and told them to change the diff fluid and update the PTV+ software. Got a call yesterday and was told that the software is already updated [saving me money] but that the service manager determined that it needs a new transfer case [!]. Although the one that was in there had less than 500 miles on it, Porsche is putting yet another transfer case in under warranty and I am told that that will fix the rumble....

CarGuyNVA

So they didn't try just changing the rear diff fluid, or they did?

Hmm... others (including yourself) have had new transfer cases that didn't seem to correct this specific noise. I still think based on what I've read of others experiences, it's just a trait of the PTV system and is kept in check/minimized with more frequent rear diff fluid changes with the proper fluid.

Well, please keep us updated, much appreciated.