Hi guys, I bought a 2014 cayenne Turbo S from someone on this site, absolutely love it. I have just over 61K miles. But have noticed I have an odd stutter I guess to call it. I’ve seen post about “grinding” it doesn’t appear to be grinding to me. Basically as I get going from about 20-35 mph as I accelerate I get noise and you can feel it in the pedal. It’s like a stutter or slipping for traction. I have suspicion of possible rear diff motor or bad rear diff, has anyone else experienced this? No codes, no leaks, any recommendations or diagnostic tips? Thanks

 

Unfortunately, like many others have experienced, it's likely the transfer case. Try swapping out the fluid with DTF1 (Shell TF0870) fluid and see if that helps.

- John

 

I know the fluid has been done not long ago but I’ll check the paperwork. From what i had read it doesn’t seem like the typical transfer case thump

 

You can try unplugging the module and going for a quick test drive. Don't exceed 30mph though as it's not meant to be driven long unplugged. Just for testing.

- John

 

ok, are you referring to module for transfer case or motor for rear diff?

Thanks

 

Transfer case. I find it odd that a rear diff would go - those are pretty stout.

 

it’s definitely possible it’s transfer case, just didnt seem like the traditional symptoms. I had read issues with the clutches going bad in the rear with similar symptoms.

 

No, the rear PTV+ diffs frequently wear out, too. It's just a less common option versus the transfer case that's in most every 958, so it might "seem" like they are stout, but they all wear out like the original transfer case clutches.

Regardless, diagnosing this is incredibly basic and has been discussed ad nauseam on this forum: unplug the control unit of either the PTV or the transfer case to rule out one or the other. Far more effective than soliciting opinions on the internet. It can't be any easier to figure out than that!

 

Was not aware that the PTV+ diffs can wear out. Is the preventative measure the same as the TC? Regular fluid changes?

 

which is what my concern was. Not sure the last time rear diff fluid has been replaced. It does seem noticeably worse once temps get up after driving for a while. I pulled fuses 3/4 (rear diff) and get the fault but it appears the stutter/slipping goes away

 

What would cause the differential clutches to wear out more rapidly than a regular diff clutch? PTV+ applies rear brake pressure to the inside wheel to achieve optimized yaw. If anything, this would wear out brake pads and tires more rapidly than a non-PTV+ car, but I don't see how this would place any added stress on the differential clutch packs themselves as long as fluid is kept in good order.

- John

 

The non-PTV+ differential has no clutches; it's just an "open" gear differential - same as the front.

The PTV+ differential has clutches that are constantly providing lockup during different situations, similar to the transfer case which is always changing its lockup (=torque distribution) based on the driving situation. The PTV+ option involves software that manages the braking in corners, AS WELL AS lockup of the rear differential clutch packs to alter torque distribution. As a bonus, the option also allows manual locking in the third off-road mode.

 

Yes, all LSD have clutches - I had misinterpreted you saying that these are harder on LSDs than other cars vs. Clutch packs wear out over time. Good news is that instead of having to buy an entire new LSD you can replace the rear diff clutches relatively easily with the right tools. Simply remove the clutch pack carrier from the diff.

If you replace the bearings, that will require checking lash and such, but clutch pack replacement is fairly straightforward.

Here's a kit from Racingdiffs.com (https://racingdiffs.com/products/por...iff-repair-kit). They're great and can walk you through replacement if you have any questions.

- John

 

Dealers says transfer case. I’m 8 months past the 10 years so I reached out to Porsche goodwill for assistance but I expect I’m kinda sol here, but worth a shot

 

No luck on goodwill. Just going to bite the bullet and get the transfer case replaced.