Hi,

My car is a 95 993. It idles nicely with no surging, pulls well, and I averaged 22 mpg on my 680 mile trip to the Monterey historics. However, I can feel and hear a slight vibration when reving past 4200 to 4500 rpm. Past that point is goes to red line very strong without the vibration/resonance. It occurs about 95% of the time in all gears. It also happens with both AC on or off. If I pull any of the vacuum tubes going to the manifold two days after running the car, I can hear a sucking/ popping sound indicating that there was still vacuum in the system.

I have done a few searches on this topic, but, still looking for answers and suggestions.

I'm all ears for any advice, etc.

Thanks,

Michel

1995 993 with 108000 miles

 

sounds like the vibration is not speed related so...

Can you feel a corresponding vibration in the shift lever?

How many miles on the flywheel?

Possibly the DMF (dual mass flywheel) failing

 

bad motor mounts also have been known to be a reason for this. For me, the motor mounts were sagging and sending vibration through the shifter.

 

Vibration is engine speed dependent, no doubt, not vehicle speed. The vibration cannot be felt in the shifter, its more through the body but mainly from engine. Original flywheel and motor mounts.

 

In this case, I would go for either of the suggestions above...

Time for a LWF/RS clutch. You'll never have to change the clutch again: it is the same as the GT3 unit:roflmao

Ooops, just a friendly suggestion. Have you thought about becoming a member? Good value

 

+993 on that.

Best money spent. Period.


Ken

 

Thanks for the suggestions, but, my car runs perfect except for the said vibration. My wrench says the clutch is holding nicely. I have tracked the car recently with no problems, smooth as can be except for the resonance. I like not having any noises from the transmission. (I am familiar with the low rpm acceleration/startup gear noise from the 915 tranni) so will stick with the DMF setup when I need to replace. Will look into the motor mount replacement. Wonder is the drilled airbox may have something to do with it?

 

Modifying your intake box won't make the engine vibrate.

 

Check you a/c lines to see if any of the attachment points are loose. Believe it or not, these can make the car vibrate at certain RPMs if they are moving around.

Also, in addition to the motor mounts, take a look at the attachment point for the transmission.

Cheers,
Joe

 

+1. A wrench (no longer in business) for my first 993 forgot to re-install one of the mounting bolts to the a/c compressor when it was replaced and the vibration occurred under similar circumstances as you're experiencing.

 

one last note on the clutch/flywheel: The clutch does not have to slip for the flywheel to be a problem.
Engine mount is an easy first step.

 

- Engine mounts changed, and vibration is still there if not worse
- Removed air conditioning belt, fan and alternator belts are correct Porsche part #s and look good.
- Help

 

Sounds an awful lot like a failing DMF, or maybe pressure plate.

 

I had a resonance but it was not emanating from the transmission. It occurred at low speeds, high torque. It ended up being one of the rear bumper cover heat shields vibrating against each other.

 

still sticking with my original educated guess
DMF failing, especially if it seems to be getting worse.

Still no vibration feel in shift lever?