2013 CTT, ~36k miles, Houston TX, function12

Is this all because Porsche lightened the 958 TC?

So, the transfer case was replaced. Car is fine now, even smoother than when new.

The tech said the case will go back to Porsche R&D for them to see why it failed. He also said moisture may have gotten into some of these units, which is causing failures.

This is a part which is supposed to last the life of the vehicle. Or at least last a long way into the life of the vehicle. Units that are failing at 15,000 miles or 35,000 miles were clearly defective from the get-go OR broke as a result of the defective (i.e. crappy) oil as noted in the posts above.

Q: Is this transfer case made by Aisin? I seem to recall reading that somewhere.

No...

It does go back to Porsche - but I suspect R&D is never going to see it. It's not like it's something new happening.No - I believe it's made by ZF. The transmission is made by Aisin.

2012, V6, 38,000 Southern California USA, steph280

I am leaning toward the moisture contamination through vent hole theory. My issue started appearing last month after the record breaking rains that we had over couple weeks. Coincidence or not, the fact that Porsche relocated the vent location higher could be an indication that contaminants are getting through.

Steph, has this been resolved? New transfer case or new oil?

Replaced?

Replaced from we have been told. Still don't have it back from the shop yet.

Did a bit of thinking on the TC vent change.

The design of the air-cooling scoop under the transfer-case is such that it would work equally well as a water scoop if you went though water deep enough to reach it. It is the lowest thing under the car. You can easily see it if you lay down next to the car and look under - it's the thing sticking down to the rear of the plastic belly pan about 3" below the level of the belly pan.

We are probably safe in assuming Porsche puts that on to cool the transfer case. That would mean they knew it was going to get hot - and hot enough that it probably needed to be cooled. I don't know if it's only on the Turbo, or if it's on all the models. Perhaps people could check theirs and report back.

That's where the law of unintended consequences struck. The cooling scoop would tend to also scoop water up, directing it to the output area from the TC for the front drive - CV joint and driveshaft. Since those would be spinning if the vehicle is moving, the water would spray off the area, and some would end up going upward - to where the vent is located. And since the vent isn't really sealed - chances are some water might get into the vent and into the TC oil. Eventually the water should evaporate out of the oil if the case gets hot enough, so prior water contamination may not show on an oil change.

That's what they addressed by moving the vent up higher in the engine compartment, and adding a slinger to the front output of the TC.

Oh - one other thought on the air-scoop. It is going to be ineffective on a vehicle where one or more wheels are spinning and the vehicle isn't moving or is moving slowly. I've certainly seen that situation on videos showing Cayenne's being used off-road. That situation is almost certain to create a lot of heat in the clutch assembly, that probably causes rapid oil damage.

That or water contamination - or both - might be the reason for early failures of the transfer cases. We don't know for sure - but I bet Porsche and ZF do. They're just not telling us, except by changing the oil used and the vent system.

Be interesting if the shop could provide you with a sample of the oil in the old case.. I'm sure they have to drain it before shipping it back to Porsche.

Hi All,

New to the site but having the same issue on a 2012 Cayenne S with 18K. Started a week ago with what felt like hesitation at low rpms but now the "thunks" have become more pronounced. Called dealership today and they said "transfer case" over the phone. I am bringing it in tomorrow to have it diagnosed. Though, Im thinking that regardless of the diagnosis I will request a transfer case fluid change first.

Thank you for all of the informative posts.

I meant to add. Please let me know if there is anything else i should try other than the transfer case fluid change prior to replacing the whole thing. Should i change the differential fluid as well?

It certainly wouldn't hurt to change the diff fluid in both differentials (there is a front and back one) - but that doesn't seem to be the issue. The issue is the clutch in the transfer-case misbehaving and a fluid change seems to put it back in order.

Try to capture a sample of the fluid coming out.. be interested to see/hear what color it is and what it smells like.

And please DO come back and tell us the results.