924Board.org

Duncan · Posted: Tue Jun 14, 2005 9:42 pm Post subject: driveline judder

I have exactly the problem described in this post;
http://www.924board.org/viewtopic.php?t=12346&highlight=clutch+judder

after driving in really heavy traffic in warm conditions, the judder
begins. I find this phenomenon very scary

.
Clutch is 1 year old. clean and properly adjusted.

Haynes says engine mounts or under engine shock absorber.

Any new insights ??

Thanks in advance,

Duncan

Slam · Posted: Wed Jun 15, 2005 4:39 am Post subject:

I've got the same problem. Car has spring-centred clutch, so I ruled that out. I know the rear main oil seal leaks a bit, so I figured that might be it.

However!

Check out FR Wilk's website - he's got some interesting things to say about 944 judder. Apparently it's more of a computer issue than a mechanical one. Early fuel cutoff as motor returns to idle. DME tweak for North American emissions. Try FRWilk.com or check out PelicanParts.com - he's on there sometimes.
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'88 944 Auto - may or may not resurrect

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

In a normal 924, it is very unlikely to be the "under engine shock absorber". If that is what I think it is. I'm speaking of the non-descript tube that hangs down off the side of the block near the alternator. That thing is just dead weight and does nothing to limit the vibration of the engine. I'd love to talk to a Porsche engineer about why it was ever installed (I guess I might have to talk to an Audi engineer).

It could be the motor mounts. Maybe in hot weather your fans kick in and you are running AC, which sends your rpm down to a lower than normal idle (which is not being compensated for by the idle stabilizer "black box" on the driver's side front fender well...another issue). The motor mount problem is really apparent at lower rpm ranges, so you might just be dipping low enough to make the engine judder on the mount(s)...
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1987 951 - M193 Version for Japan

Duncan · Posted: Sat Sep 24, 2005 6:17 am Post subject:

I think I have made a more accurate observation now. If I select first gear and from a standstill just let the clutch came up a little bit, and keep it like that you can feel the judder come up. At first it isn't there, but slowly you feel the amplitude go up. When you drive away in the normal fashion, this 'clutch partially engaged phase' is very short, but when you want to 'creep ahead' in a traffic jam it takes longer and the judder amplitude becomes large. Can anyone more precisely identify what the source of this phenomenon is? Clutch has been checked recently for cleanness.

Duncan