Vibration on Overrun - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Troutman · 09-30-2013, 10:25 AM

I get a slight vibration/rumble sometimes on the overrun. It's not harsh, more like when you drive over a rough road surface. Except it's happening a super smooth tarmac.
Could this be engine/gearbox mounts starting to fail?

BYprodriver · 09-30-2013, 02:39 PM

I don't know what you are driving but if it's a 986 & the front engine mount has never been replaced with the improved 987 version, it needs to be. Look for fluid leaks from the trans mounts & replace if fluid is leaking.

Nimbus117 · 10-02-2013, 12:04 AM

As above. Mine vibrates between 3200-3000 on deceleration every time. Will get mine done when I have the clutch replaced.

Troutman · 10-02-2013, 07:31 AM

Quote:

Originally Posted by BYprodriver

I don't know what you are driving but if it's a 986 & the front engine mount has never been replaced with the improved 987 version, it needs to be. Look for fluid leaks from the trans mounts & replace if fluid is leaking.

No fluid leaks but it sounds like that might be the problem.
It's a 99, 986 2.7. 65k miles

I didn't realise the trans mount had fluid in it though.

papasmurf · 10-02-2013, 08:15 AM

mine did the same thing right around 3k rpms....never could really feel it accelerating but could feel it through the bottom seat cushion from time to time when coasting or when shifting gears around that rpm range....my mileage was probably around 60k when I replaced it.

litespeedp · 10-02-2013, 04:56 PM

Had same vibration at around 3000 RPM just like everyone here on my 60,000 mile 2000 S with manual transmission and replacing the front engine mount was the fix!

nieuwhzn · 10-02-2013, 08:09 PM

Yup, have fun with replacing the engine mount.
Btw, the Boxster flat 6 engine does have and eigenfrequency at about 3000rpm and you will feel some more vibration at those rpms when the engine is unloaded, even with a perfect engine mount.

teleski · 10-03-2013, 11:48 AM

Long Island, eigenfrequency... perhaps you work at Brookhaven (or Stony Brook)?

nieuwhzn · 10-03-2013, 08:10 PM

Quote:

Originally Posted by teleski

Long Island, eigenfrequency... perhaps you work at Brookhaven (or Stony Brook)?

Ugh, should choose my words more carefully...you found me out.
Working for MIT actually, stationed at Brookhaven since 1999.

teleski · 10-03-2013, 10:57 PM

Quote:

Originally Posted by nieuwhzn

Ugh, should choose my words more carefully...you found me out.
Working for MIT actually, stationed at Brookhaven since 1999.

;-) I spent a summer at Brookhaven in the mid 80s while in college. Spent half the time sweeping the pit while they constructed BNL-787, the rest writing Fortran code on a VAX teletype terminal. Great times.

sb01box · 10-03-2013, 05:14 PM

Quote:

Originally Posted by Troutman

I get a slight vibration/rumble sometimes on the overrun. It's not harsh, more like when you drive over a rough road surface. Except it's happening a super smooth tarmac.
Could this be engine/gearbox mounts starting to fail?

Been reading this thread and trying get the definition of "overrun" can you educate me?
Thanks in advance