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Engine Vibration at 3100 RPM

I just recently replaced my clutch on my 02 Boxster. Everything went perfect thanks to Wayne's outstanding DIY writeup. Now I'm pretty sure that prior to this clutch replacement I didn't have a vibration at 3100 rpm but I sure do notice it now after the clutch replacement.

I double checked the transmission mounts to ensure that everything was torqued properly and still have this vibration... Does anybody think this could be bad motor mounts and completely coincidental or should I dig deeper into my clutch replacement job?

Thanks and much appreciated
Old 01-29-2012, 09:39 AM
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Quote:
Originally Posted by jayweitekamp View Post
I just recently replaced my clutch on my 02 Boxster. Everything went perfect thanks to Wayne's outstanding DIY writeup. Now I'm pretty sure that prior to this clutch replacement I didn't have a vibration at 3100 rpm but I sure do notice it now after the clutch replacement.

I double checked the transmission mounts to ensure that everything was torqued properly and still have this vibration... Does anybody think this could be bad motor mounts and completely coincidental or should I dig deeper into my clutch replacement job?

Thanks and much appreciated
did you remove the flywheel? did you torque the pressure plate evenly? did you check your dual mass flywheel if it is worn ?
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Old 01-29-2012, 10:01 AM
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harrytrcb.

No I didn't replace the flywheel since it was still within the spring back specs. I also torqued the pressure plate evenly (snugged each one up in a cross pattern, then torqued in a cross pattern)

thanks
Old 01-29-2012, 10:08 AM
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also more clarification on the vibration. It is slight but noticeable only at 3100 rpm. by the time I get to 3200 it evens out. Feels like a harmonic vibration very similar to my sons jetta MK4 before we replace the motor mounts. Hence why I'm leaning in that direction. Just don't want to start throwing $$ at a problem before I know what the problem is.

thanks
Old 01-29-2012, 10:10 AM
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a search at 986forum (and probably here) will show lots of talk about the 3k vibration. i have it too. some say it is drone from their exhaust, some say it is deterioration of the dual mass flywheel, some say it is a failing motor mount. depending on what you read, folks have either successfully or unsuccessfully addressed the drone by fixing one of the above. the official porsche position is that the car is supposed to do it, so no help there. you may have distrupted any one of the above with your clutch job, so those are the places i would start to look. if would suck great bowls of suckiness if it was your flywheel what with you just having been in at your clutch ...
Old 01-29-2012, 10:40 AM
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I believe your '02 will have the earlier designed motor mount which is very prone to failure. Mine was in bad shape at 84k miles and also created the 3k vibration. I'd start there since the upgraded part is fairly cheap and job is not too difficult to do.

Steve
Old 01-29-2012, 11:14 AM
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Do you get a (Clunk) when shifting hard, or accelerating/decelerating?
I just finished a clutch job on my 05 and don't have a bad vibration at 3K but am now noticing the clunk. (I don't think I could have felt it before due to the clutch slipping so bad)
Since I checked my transmission mounts, I am going for my motor mount.
Good luck!
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Old 01-29-2012, 04:13 PM
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It might be that your front engine mount was starting to crack and with all the engine wiggling doing your transmission it cracked some to the point you now feel a vibration. Donno just a thought.
Also how many miles do you have on he new clutch. I just did mine and have a couple hundred miles on it and now it is so smooth. Not sure if there is a break in period but mine at least now feels great.
Old 01-31-2012, 05:04 PM
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Change your motor mount

In a bid to improve my shift action, last year I replaced my 01-design motor mount with the latest design mount. The shifter action didn't improve any, but my 3000rpm vibration vanished, like magic!
Old 02-01-2012, 03:39 AM
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The motor mount is the likely culprit but I have seen some funny stuff with the rear catalytic converters as well. I have installed bypasses on these cars and that vibration magically went away.
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Old 02-01-2012, 10:07 AM
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Thanks everybody for the comments. I have decided to replace the motor mounts. I agree that with the movement/jacking/supporting the engine to remove the transmission that is has probably cracked/messed up these mounts.

I'll post a status after I have done this replacement in a couple of week.s
Old 02-06-2012, 09:15 AM
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also I have about 200 miles on the new clutch now and the vibration still exists. There isn't any clunking or weird sounds when shifting. Everything is as smooth as the day I bought it (now after the clutch change). Pedal feel as well as travel truly exhibits a new clutch feel.
Old 02-06-2012, 09:17 AM
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I used to have the same 3100 rpm vibration, especially on coasting and part throttle. Never under acceleration or WOT. About 6 months ago i bought a $250 aftermarket muffler (Chineese, but OK), not only did the vibration disapear, but I also gained 100HP on my butt dyno (at least it sounds like 100HP more, like a GT3!). So the vibration is a sound resonance around 3k rpm.
Old 02-10-2012, 07:15 AM
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When I experienced this long time ago on my 2000 base tried a few different ways to get rid of this. First step was of course the motor mount but it didn't help.
Next step was the flywheel, no change here either.
But once when I changed to a S muffler I noticed a change in the amplitude of the vibrations. So I tried to mount it on different heights an with pretension in the pipes with the help of a hydraulic jack and depending on this pre-tension it became better or worse but not perfect.
Then I bought bypass pipes and voila, the vibration came at 3500 rpm instead.
Guess it was the lower weight that made the vibration to show up at a higher frequency.
Finally I bought the most recent motormount from the 987, really soft. It cured the last vibrations but instead I do get a feeling of the engine moving around, probably just imagination.
Old 02-10-2012, 10:11 AM
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Problem fixed!!!

Well today I got around to installing the new motor mount. After some jiggling around and lowing the engine to the right distance I was able to remove the mount/bracket.

Upon removal it was quite easy to see where this vibration was coming from. The old mount was completely cracked all the way around and was quite loose in the bracket.

Installed the new one and once everything was put back together, I started the car and revved the engine up to 3100 and whoa-la no vibration. Took it for a spin and shifting was definitely smoother as well as zero vibration ~3100 rpm.

Thanks to everybody for all of your input.
Old 02-11-2012, 11:39 AM
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