I have 24K miles on the truck now. I had noticed over the past that there was a stumbiling or hesitation with a light clunking noise when driving at a normal speed, easing off the gas, then re-applying the gas (not stomping on it). At the 20K service I called it out and they found nothing. Yesterday, driving back from Bend (great snow drive by the way), a friend was driving and he said he noticed the same problem. Has anyone noticed a similar problem?

 

There have been reports about cardan shafts doing this (defective rubber in the original assemblies).
The hesitation sounds DME related, not mechanical.

Otherwise stuck brake caliper/pad? There have been reports of this, but normally when backing up and applying/releasing brakes.

I'm surprised that once up on a lift, they couldn't quickly do the mechanical check and if the engine is missing at low end, the DME should log an error or two and report it via PIWIS.

 

I noticed this particular issue when accellerating on a curved on-ramp to the interstate .. when I had to slow, it would clunk when just easing up the speed to enter the flow of traffic. I reported this several times and it did clear but I forget what they claimed to be the solution. All my service records are at my office in a 5 foot thick file (ha!) and I'll see if I can locate.. If memory serves, it may have been "gone" after they replaced all the ignition coils which were cracked underwarranty.. do you have some rough idle at times? if not, you may be starting to get zee dreaded coil crackz... documented problem and it may be the culprit. cardan shaft also but it seems to be fairly rare.

 

Thanks for the input MF, I mean Madfox, my friend thought it might be u-joint(s), but there is a definite stumbling and clunking (that I have tried to induce unsuccessfully) so will appreciate any info you might have. Still love the truck and it performed flawlessly (except as noted) on a snow-packed 100 mile drive. The PSM kicked in one time when I was passing a car. It continues to put grins on my face and passengers!

 

I will see if that is what they blamed tomorrow and try to remember to post... Signed MF

p.s. uh-hum.. The only downside to MadFox as a "net"-name is the abbreviation can be made into MF.. however being a Navy guy.. it is proper to put a "BIG" in front of it... because when pushed into a corner by young turks driving 150mph and nearly killing me or my family on the interstate -- they will know that it is an apt shortening of the moniker (and my .45 with me will help to prove the point!)

 

This could also be a sign of lash in the transmission, I would report it asap to the dealer for investigation.

 

Okay, Jimbo from Portland Airport Code: I went through my five foot thick service record file and each mention of clunk or lurch when driving as you are experiencing that I made there was an "unable to duplicate" and a note that the latest version of software was already installed.. I reported it 6 times from under 10K to over 40K miles.. 46K is when they replaced all plugs and all ignition coil caps due to cracks.. so I think either mudman is right or you have the cracks.. I do not have this issue anymore. Get thee to the service dept! BHMMF

 

I would like to know if Jimbo from Portland ever resolved this issue as it describes my 04 CS precisely. It has bothered me since 15K miles (currently 21K) and I have had it in the shop no fewer than 6 times to resolve it. Admittedly, some of those times they ordered the wrong part, so it doesn't really count as an attempt to fix does it. I am going in tomorrow for my third transmission control unit--one specific to my VIN number (I am not sure what they put in last time??) Not a high likelihood of success I would guess. Having read this thread, I did mention the ignition coils last time to the technician who seemed to dismiss it. I do get the rough idle problem as well, so I am going to print this thread, highlight it, hand it to them, and hope for the best. Wish me luck and thanks for the advice.

 

I took the car in for clunk when going in reverse last month and the invoice states "found slight play in driveshaft". This was explained as "nothing to worry about, but if it becomes uncomfortable (what he meant by that I don't know) bring it back in". Coils were supposedly checked and found to be in great condition. I am bringing the car back in tomorrow because the clunk now appears at low speeds pretty much identical to MadFox's description. Now, question, "play in driveshaft" is the same as cardan shafts that you mentioned? Thanks in advance.

 

Deterioration of the rubber mounts on the shafts could be a possibility, however I would have thought it would 'clunk' in both directions, not only reverse. Slight play should really be slight play.....they're not going to voluntarily start replacing shafts.....way too much $$ for PCNA to dish out unless they are forced to.

If it's reverse only, I would suspect your transmission....if so, it will likely get worse over time and will hopefully be addressed before your warranty evaporates and you end up 'naked'.
Again, high $$ item, so it won't be replaced until pressed....and if it is replaced, you will likely end up with a remanufactured unit.

 

It started clunking in both directions, that's why I'm taking it to a dealer, but not the one who diagnosed "slight play" since he's out of state (where I purchased). I'm bringing in the invoice that states the above, copy of this thread and let the bitchin' begin! :-D

With PSM OFF the clunk practically disappears. I MIGHT have heard it once.

Thanks for your quick response.

 

You didn't mention PSM making a difference with the clunk......you're making me work now.

Based on your latest bread crumb, I would also suggest having the DME/transmission control units checked against your VIN for the 'latest' modules.

Best of luck.

 

My "problem" was never resolved. Could not induce at dealer so, just hanging in there!

 

Soooo ... took the car to Pepe Porsche today in am. Upon presenting the sales advisor (will not be mentioning names at this point) with the invoice from an out of state dealer and a printout of this thread & was immediately told that to him, "this is considered spam", but he will check for clunk.

Came back to pickup the car only to find out that they weren't able to replicate the clunk while supposedly doing a road test. Requested for a tech to go on a road test together, and sure enough, car clunked at least 3 times. Service advisor's reaction was that "Now that this was confirmed by a tech, we will take a closer book and will actually go through past experiences of other customers to see what the fixes were". Bringing the car in next Thursday and will keep you guys posted. Tech's first response before hearing the clunk was that this might be an ABS issue related to driving on the wet surface (tripple HA HA HA) with tires slipping, but the second he heard the clunk ABS was ruled out.

Car was also in for installation of the new tips for which a new (attention: mjw930) lower rear bumper valance was ordered. It looks like they didn't charge for painting it.

 

Good to know, thanks.

BTW, the list price on the lower cover is $318. Sunset quoted me $217 That pays for the paint (well close anyway).

There's an independent body shop guy that works out of my dealers sister Mercedes dealership that is supposed to be able to work miracles with plastic bumpers. I'm going to get a quote from him before I do anything.