jyoteen

Getting a noticable vibration on off throttle, in gear (usually lower gear like the unappreciated 4th) vibration through the car at deceleration from 90 or so mph. It can possibly be in a lower gear and lower speed (like 2nd and 45 mph) but I haven't tested that yet. The vibration seems to be originating at the rear (possibly passenger side, but not positive on the actual left/right part).

No vibration accelerating to 90 mph or more.

Car is only on 2nd wheel bearing since new.

Clutch has about 55-60k miles, which is frankly amazing because in the past, i've not gone more than 40k miles on a clutch.

What could it be?

the 'Guibo' is original too.

911-140.6

I recognize your name from Quattroworld..I am Swordfish on there. When was the rear diff last serviced ?

Paul Waterloo

If it's only off throttle, I would keep testing it and see what gears it happens in.

It could be the "coast" side of a gear is starting to fail. As swordfish states....you could always change the gearbox fluid and see what kind of foreign material comes out, if any. If you have metallic particles, something is letting loose.

Jyoteen and swordfish.....know you both. Too funny.

fillzplace

I just had the Guibo (flex disk) replaced on my 2004 C4S and it got rid of a similar vibration that I had. It was done at the same time as replacing a leaky front differential seal, so it seemed the perfect time to address it.

When I purchased the car a little over a year ago there were notes in the service history that the flex disk was cracked and needed replacement (going back to 2010), so I decided to have it done as a preventative measure. It turns out that the disk was is bad shape by the time it was finally changed about 3 weeks ago, and there was a noticeable reduction in vibration when letting off the gas - at all speeds. I didn't really realize how much vibration was there until it was gone, so a noticeable improvement and worth the $80 part.

If you can see cracks in the flex disk, replace it. As my Indy says, 'it didn't come from the factory that way'.

silotwo

Interesting - I have a vibration on decal in my C4S as well. It's rpm dependent rather than speed dependent. 2nd, 3rd, or 4th gear on throttle to 5k rpm or higher and the vibration kicks in on decal at about 4600 rpm and goes away at 4200 to 4000 rpm. Of note is that it only happens when the engine is at operating temperature. Also seems to originate from passenger side rear and is felt through out the car. Very consistent and easily replicated.

Replaced motor mounts no change.
Having the Guibo disk replaced later this week.

Paul Waterloo

Now that I looked up Guibo disc, I see that would most likely be a common issue. I would recommend performing a detailed inspection or potential replacement of them. Looks easy.

5CHN3LL

Worn transmission mount?

If you're going to go through the trouble to pull out the old guibo, spend the extra half hour and junk the FWD stuff. Lose some weight, and get a hearty helping of that "OVRSTEER" your license plate mentions. I'll never go back.

911-140.6

I actually just saw your AC woes thread on the D3 board a few days ago..

FRUNKenstein

Paul: Is that something you'd need a microscope to do?

jyoteen: If you haven't changed your motor mounts in the past 5,000 miles, the conventional wisdom on here is that they are overdue and will dramatically improve all aspects your life.

alpine003

Just like we have a IMS tool loaner program setup, Paul really needs to get on the ball and setup a Microscope loaner program. IIRC, the model he has can even one up Blackstone Lab's...

jyoteen

The car's fluids (all of them that aren't motor oil or brake fluid) I have religiously purged all fluids every 2 years.

So transmission, coolant, etc are all new regardless of mileage due to track use.

jyoteen

Hi Paul,

I sure hope it's not the transmission, except I wouldn't be totally surprised since I have 152k miles on it with a lot of track miles with the transmission never been rebuilt.

I don't have difficulty shifting up or down. Still smooth, but just maybe the coast gear as you indicate. Will swap fluids first, of course.

jyoteen

Actually, I just changed my motor mounts last year, if I remember correctly. However, I have heard that the motor mounts do not take kindly to jacking up the car from the center seam right behind the engine case as I have had to do to get jack stands under the car. So maybe they're prematurely toast?

But I don't get any other indication that the motor mounts are on the way out.

jyoteen

Please post your update, as my suspicion is the gumbo, only because everything else really on the car has been replaced and all fluid service is also pretty current.

Porsche does not sell the guibo flex disc by itself (have to replace the shaft too), so let me know of the costs if you do find the guibo disc by itself and part number. I know people have suggested using a BMW part but that is different.

If it is the BMW part, I get that at cut throat work related discount.

fillzplace

Pelican Parts -

10-2539-005-M57 $94.75 1 $94.75
Driveshaft Flex Disc Brand: O.E.M., Brand: O.E.M.

It may be the same as a BMW part, but not sure.