Slow start thump...

[deepraver]

From a slow (typical) start from a light or other stop the '04 Cayenne in a few feet (1-2 car lengths) I get a loud thump from the undercarriage. This is the only time it does it. Nothing is obvious underneath.. Any ideas?

[bmats]

I have the same thump and took it to a local porsche garage (not the dealer), after spending $155 to diagnose they gave me a copy of the TSB dated April 18, 2006 that is titled "Noise- from the front end of the transfer case"...just goes to show information is valuable. The TSB recommends the replacement of the transfer case control unit and the garaage quoted me $750 to install.  Suncoast parts has a repair package named "PTM Transfer Gear Servo Motor Update" for $1072.82 , however, it comes with a new gear servo motor. I contacted the parts department and they say that this is a package deal because this is the recommended repair, my local repair guy disagrees and  says that just the control unit needs to be replaced.. When I asked Suncoast how much the control unit would be by itself, they quoted $350+ tax and shipping...and emphasized no refunds. In speaking with the local repair guy, and asking my strategic questions, he said the replacement is a simple plug and play and is accessible from under the passenger seat. Sounds like a total DIY taks...I haven't gotten around to doing this myself...however, now that it's back on my mind (because of your post)  I think I'll go ahead and order the transfer case control unit and replace it to see if that resolves the fix...I hope this helps you out. 

 

Here is the link to the part package at suncoast: http://www.suncoastparts.com/product/955PTM.html?Category_Code=CayenneS_Enginetran

[deepraver]

Thank you for responding!  Yeah, if you read this below from the Suncoast site it says the motor is overheating after long distances... my thump is happening cold and not going away or getting worse with miles driven so I would agree the motor is not at issue... When are you planning on doing this? I definitely am interested if your noise goes away and was the same.. from cold on... 

 

PTM Transfer Gear Servo Motor Update

 

Display in instrument cluster: "All-wheel drive system defective" - For fault code 2033, 2039, 2041, or 2042 in transfer gear control unit.

When the transfer unit is diagnosed as being defective, this parts kit updates to the latest version as recommended by Porsche in a technical service manual.

In effected vehicles, the servo motor overheats while in "Low Range" driving program after driving long distances due to a fault in the transfer gear control unit. To complete this update, a new control unit for the center differential lock and new servo motor are required.

This upgrade is for 2003 to 2009 Cayenne, Cayenne S, Cayenne GTS, Cayenne Turbo, and Cayenne Turbo S models.

[deepraver]

So here we are.. I replaced the transfer case control module to the newer version (PorschePartsHub.com 369.33 shipped) an easy DIY. You do have to remove the passenger seat to get a the front screw that holds it in. 90% of the problem seemed to disappear. The thumps became infrequent and less harsh, but still remained. So I went with replacing the motor. I had my mechanic do it because I was having health issues and it ran me 439.64 for the motor from World Pac and the normal labor charge... The thump is still there. Any other ideas?