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Anybody know anything about this:

'04 Cayenne S with 28k miles - pulses when making turns, especially in reverse and when the steering is fully locked, but only when its hot. It feels like its got huge mud flaps or like it being driven by giant gear cogs.

Took it to the local dealer on a hot day. They put it on the rack and wiggled CV joints by hand, nothing felt out of order. After a test drive the mechanic said it was normal Cayenne behaviour, but it feels awful, like its going to seize. And the problem is getting noticeably worse. It shows up on simple turn-in when the car is fully hot. Could this be brake pulsing from the ultrasensitive PSM? Or maybe the traction management system has a problem?

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Have the dealer look at the differentials and/or the mechanism that makes them lock. It sounds like the center differential is locking partially or fully when hot. That will show up on hard pavement as a pulsing or, when it gets really bad, a popping feel. When the diff is locked on a hard surface then in tight turns the wheel swill build up a torque difference between them which makes the steering wheel jerk a little or the tires pop as they equalize. If it goes on too long you can thrash the differential entirely...which is why you should be unlocked on hard surfaces. If you have the offroad package then you may have a locking rear diff but otherwise IIRC there is only the center diff that could be locking. Since it happens only when hot I would guess that it may need to be serviced but is probably not critical.

One way to confirm it (close enough anyway) would be to find a nice smooth piece of concrete, the kind that makes your tires squeal when you turn on it, and drive in a slow tight circle. If you hear a regular chirp, chirp, chirp from the tires as you go round then either your front or center differential needs service. Try clockwise and counterclockwise.

Happened on my Range Rover when the center diff, a viscous coupled unit, wore out. The fluid went bad so it began to progressively lock over about six months until I had to replace it. Same story for any 4wd/awd.



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  • 3 weeks later...

Thanks for the feedback! Good news is - after a week in the shop and a new stepper motor in the transfer case, the problem is gone.

Bad news is it took a week to convince the dealer to put a new stepper motor in to fix the problem. They were unsure about what to do until I did some research on the Touareg and found out it's got the same problem. See:



According to my dealer Porsche has no "campaign" on this extensive problem so they were reluctant to do anything. This was even after a Porsche service rep looked at the problem! During that week they replaced all 8 cracked coils, tightened a loose cross member on the transfer case, and loaded new software for the transmission. None of these actions stopped the "shuddering".

The stepper motor engages the diff lock and apparently often fails in an intermittent way that causes shuddering on hard turns. There is a new revision of the motor but I would still watch out for this problem on all Cayennes. It's not a catastrophic event but it causes binding which will put more wear on tires and other drivetrain components.

What would we do without forums?


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There was an action in Europe for the stepper motor !

Really! I searched the PCNA TSB's on Renntech.org and could not find any mention of a campaign for the transfer case stepper motor problem. Does anyone know of a campaign for the stepper motor here in NA?

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  • 6 years later...

I guess i am on the list to replace the stepper motor. Looks easy to install.

Guess they are on the second generation. Here is the latest part number i could find: 955 624 601 01

Used for $200 and new for $500 plus. Don't think a used one would be a good idea.

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  • 5 weeks later...

Found a stepper motor from a 2008. Figure it will be a second generation motor and the price was super cheap ($150) so if it lasts only a short time it would seem worth while. Some interesting things…

The motor on my transfer case was made in USA. I went to their web site and they have a brochure that has a picture of a Cayenne. Could this have been a factory part? I don't have any records of my motor ever being replaced but i am the 3rd owner.

The other thing i noticed is that the motor has a planetary gear system. It had no grease on the gears. None. Seems weird that they would build it this way with no lubrication. After taking it apart i could only come to the conclusion that the plastic sensor on the front must have gone bad. The motor and gears all looked good. When i installed the new used motor i didn't have any symptoms like before. So this issue is fixed for now. Hope the made in germany part holds up better than the made in USA.





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  • 6 months later...

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