Cayenne TT, 2008, PDCC + air suspension lowered, 21" and 19" wheels
Here is my issue:
Rumbling vibration @ max under slight acceleration! Described as 50-80hz vibration in dashboard and steering wheel (steering wheel is vibrating NOT shaking). Partly it could be felt through the seats as well. Probably a Grand Cherokee on mud/off road tires has similar vibration
SPEED: 70-105km/h
GEAR: 5th and 6th
RPM: generally Below 2000 (1600rpm = max vibration)
Sound: no definite whine or any noise/sound related to the vibration!
When I lift off the vibration reduces greatly (still there but could be described as no vibration).
Up until now the vibration is proven NOT to be from:
Wheels and tires (different set = same vibration)
Cardan shaft (brand new)
Short cardan shaft (checked on balance machine)
Front CV axle shafts (checked on balance machine)
I am left with not many options but:
AT Gearbox - Torque converter or friction discs (Lubegard additive on the way for diagnostic purposes)
Front Lower control arms (heard/read about cases where similar rumbling vibration was felt due to excessive play in rear bushings).
Please share your ideas/experience and ask me as many questions as you wish!
HELP ME! I am tired of this

 

Had a similar mystery vibration.
My situation was caused, I believe, by build up of brake dust inside the front rotor’s vents.

I tried everything to find this vibration and gave up - only to have It vanish when I installed fresh rotors to replace worn ones.
Assuming one of the rotors was the issue all along, I did nothing different and over time the vibration returned.
Cleaning the inside of the rotors and keeping them clean helped but never eliminated the vibration like the fresh rotors had.

When time came to install a 3rd set of rotors, I swapped to low dust pads and never allow the rotors to get very dirty… she’s still smooth as can be.

 

Every time I get rumbling vibrations, i run to the bathroom. Helps.

 

In between I have changed the rotors + pads. Nothing there!
I should probably try a NVH diagnostics. Might catch something.

 

Hey...I have EXACTLY the same problem!!! Also a 957 2008 CTT (build date late 2007).

I've checked the same possible causes as you have and have done the following

• new upper and lower front control arms because the LBJ rubber was perished and I stupidly thought it would sort the vibration problem.
• I've had the wheels balanced at least 5 times + new tires all around.
• New spark plugs and coils (genuine Porsche from ECS)
• New divertor valves
• I've been told the throttle body and MAF sensors were cleaned, but I'm doubtful of the honestly of the place that claimed this.
• New valve cover gaskets and sparkplug seals (mainly because of a small oil leak)

Sometimes I get a pronounced stutter or shuddering on gentle (not heavy) acceleation above about 50km/h. It seems to me that the 'shudder' or 'stutter' is a seperate issue from the 'vibration', and appers to 'come and go' - I've noticed that different brands/grades of fuel MAY have an effect on this??? - I actually took the car to a mecahnic yesterday because of this problem, but also a more urgent fuel leak smell (possibly fuel filter flange), and also a 'rattling' noise like a worn pulley but coming from the rear of the driver side engine/scuttle area - it was his opinon that the noise was not engine related but something behind the scuttle, anyway I'll be taking it back in a few days when the fuel level is reduced (to acess the fuel fileter flange easier) so they can check out all these issues, but the guy was 'touching' a few things on top of the engine, and he gave the crankcase vent pipe a good nudge ( https://www.europaparts.com/crankcas...810724553.html ), and now the engine MAY be smoother ...From a bit of research it may be possible that this breather hose could contribute to stuttering acceration etc...I'll have a closer look at this pipe later today to see if I can see anything obvious...

ANYWAY...After 16 months and only 10k KM of ownership (not driven much due to COVID) I've realised that the vibration, is ALSO present in NEUTRAL or PARK, at eactly (ish!) 1625RPM AND 2050 RPM. It's difficult to feather the gas pedal becuase it's quite sensative, but when you do, you get exactly the same strong vibration sensation through the seat as you do at 80 - 110 ish KMH (55-65 MPH approx)...

I believe the car has has new engine mounts (related to blown coolant pipes, I believe that access to relace the engine mounts becomes available when the gearbox is removed to access the coolant pipes, or alternatively the entire subframe was removed - i'm not entireley sure, but I have the old invoice from the previous owner showing new engine mounts in 2017).

I explained all this to the mechanic yesterday, and to be honest he seemed very unsure about it all. My current suspicion is the harmonic balancer on the crankshaft, other than that i'm clueless! Like the OP, any help would be appreciated (I'd happily pay for accurate advice!!! - actually maybe I should bite the bullet and take it to the main dealer?? - I'm in Oman - not many knowedgable mechanics here for German cars))

I hope the above might also help someone else. I'll try and keep this thread live and report what (if anything the mechanic finds when I take the car back)...Who knows perhaps the rattling, petrol smell and vibrations/stuttering are all related!!

ps. there's no CEL, and I havent scanned it lately, but I used to have a perpetual 'underboost' code, not solved by the new divertor valves (however I may have read that the codes for this can't be cleared by Durametric which is what i'm using).

Cheers

Rich

 

Hey...I have EXACTLY the same problem!!! Also a 957 2008 CTT (build date late 2007).

I've checked some possible causes and have done the following (but no crankshaft position sensor problems that I'm aware of

• new upper and lower front control arms because the LBJ rubber was perished and I stupidly thought it would sort the vibration problem.
• I've had the wheels balanced at least 5 times + new tires all around.
• New spark plugs and coils (genuine Porsche from ECS)
• New divertor valves
• I've been told the throttle body and MAF sensors were cleaned, but I'm doubtful of the honestly of the place that claimed this.
• New valve cover gaskets and sparkplug seals (mainly because of a small oil leak)

Sometimes I get a pronounced stutter or shuddering on gentle (not heavy) acceleration above about 50km/h. It seems to me that the 'shudder' or 'stutter' is a separate issue from the 'vibration', and appears to 'come and go' - I've noticed that different brands/grades of fuel MAY have an effect on this??? - I actually took the car to a mechanic yesterday because of this problem, but also a more urgent fuel leak smell (possibly fuel filter flange), and also a 'rattling' noise like a worn pulley but coming from the rear of the driver side engine/scuttle area - it was his opinion that the noise was not engine related but something behind the scuttle, anyway I'll be taking it back in a few days when the fuel level is reduced (to access the fuel filter flange easier) so they can check out all these issues, but the guy was 'touching' a few things on top of the engine, and he gave the crankcase vent pipe a good nudge ( https://www.europaparts.com/crankcas...810724553.html ), and now the engine MAY be smoother ...From a bit of research it may be possible that this breather hose could contribute to stuttering acceleration etc...I'll have a closer look at this pipe later today to see if I can see anything obvious...

ANYWAY...After 16 months and only 10k KM of ownership (not driven much due to COVID) I've realised that the vibration, is ALSO present in NEUTRAL or PARK, at exactly (ish!) 1625RPM AND 2050 RPM. It's difficult to feather the gas pedal because it's quite sensitive, but when you do, you get exactly the same strong vibration sensation through the seat as you do at 80 - 110 ish KMH (55-65 MPH approx.)...

I believe the car has new engine mounts (related to blown coolant pipes, I believe that access to replace the engine mounts becomes available when the gearbox is removed to access the coolant pipes, or alternatively the entire subframe was removed - I’m not entirely sure, but I have the old invoice from the previous owner showing new engine mounts in 2017).

I explained all this to the mechanic yesterday, and to be honest he seemed very unsure about it all. My current suspicion is the harmonic balancer on the crankshaft, other than that I’m clueless! Like the OP, any help would be appreciated (I'd happily pay for accurate advice!!! - actually maybe I should bite the bullet and take it to the main dealer?? - I'm in Oman - not many knowledgeable mechanics here for German cars))

I hope the above might also help someone else. I'll try and keep this thread live and report what (if anything the mechanic finds when I take the car back)...Who knows perhaps the rattling, petrol smell and vibrations/stuttering are all related!!

ps. there's no CEL, and I haven’t scanned it lately, but I used to have a perpetual 'underboost' code, not solved by the new divertor valves (however I may have read that the codes for this can't be cleared by Durametric which is what I’m using).

Cheers

Rich

 

About the underboost try the one way valve which is positioned on the left side of the intake manifold, connecting the PCV system (if you need a photo I could provide).
Soon I will be ready with the upgrade and there will be a replaced torque converter. I will share the outcome!

 

Will do - thanks for the tip!

p.s. left side = driver's side?

 

Yes, left side is driver side

 

Thanks SRT...I'm guessing it's item 'A', on my picture below - the vent line check valve? If so, any tests that can be done to determine if the component is functioning correctly, before I get the credit card out?

 

Refurbished Torque converter - no Luck. The vibration is still there! Interesting fact is every time I try to find it and dismantle something (prop shaft, axles, TC etc) there is hardly any vibration for a day or two. Therefore I think while we are repairing on the lift something settles in the right place (probably front wishbones). Shortly after that...everything is back!

 

Hi did you ever fix this problem? I have something almost identical!

Thanks