What are the symptoms of IMS failure?

[RS964]

Let's say that the timing is still intact and the car still idles very well and has no apparent noises coming from the engine. My father's 996 with 50k miles has a noticeable vibration when revving the engine. Upon visual inspection of the drivetrain, we noticed that the tranny bellhousing has a crack all the way around. There is a very noticeable vibration when the engine is revved past 3k rpm. Im leaning towards an IMS failure but the bellhousing has me stumped. So either the motor or the tranny is done. I suppose one way to tell is to remove the tranny and run the engine to see if the vibration is still there. Any input? Thanks.

[Britwrench]

First job is to repair the clutch housing as guessing what else may (or may not) be wrong is wasting your time. Replace the trans and check again.

IMS failure starts with engine rattles and then the engine stops, this can happen within a block or two. Had one customer drove his Boxster across a street when rattling and then it stopped, broken the timing chain and bent valves.

[johnjohn14]

Hi,I have the same problem with my 996 vibrates over 3000 rpms and broke the bell housing,does anyone know what caused this maybe the flywheel

[FPB111]

Bad dual mass flywheel is one cause I do not know of others. Post this question on Renntech.org and see if anyone has better info.