[Snufkin]

I had a good chat to my mechanic on Friday. He suggested the same thing, might be more worthwhile to pull the engine out rather than the transmission. He's going to get prices for various things, including the cam chains and then we will go from there. If I'm going to spend the money now I'd rather make sure I deal with everything I can while the car is in pieces. I should hear back from him mid next week

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[flash]

hmmm - supercharger?

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[Snufkin]

Haha I'm afraid my budget doesn't quite stretch that far!

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[Snufkin]

This is a long overdue update on my vibration issue. For one reason or another i've only just got the car sorted in the last week. 

 

So, after taking it to a couple of mechanics for their opinions, they found the flex damper is in one piece, no cracks, it's all still there. However, it may still be the culprit of a vibration at 3k rpm I haven't been able to remedy. Read on...

 

What did make a huge difference was new engine mounts. Despite replacing mine exactly a year ago and driving less than 3,000 km since I needed new ones. Last year I installed aftermarket ones, this time I paid the premium for original Porsche ones, which will hopefully last a whole lot longer for the sake of my wallet.

 
The old mounts hadn't collapsed much, but the engine is now a whole lot smoother, especially at idle. And the vibration I was feeling at 3k rpm and particularly under load is now much less noticeable. So the old engine mounts were amplifying whatever it is that is causing the second vibration. One theory is that the Flex Damper is somehow warped or out of shape. 

 

I haven't driven the car much since I got it back, yet to decide if the vibration that is left is worth chasing or if it's something I can live with.

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[WJH]

Are you absolutely sure that the balance shaft gears are on correctly? They lower is not the same as the upper.

They are easy to get on incorrectly.

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[Snufkin]

All the belts and rollers were changed while the car was getting the engine mounts replaced. I'm fairly confident the (very experienced) mechanic would have got it right. It's not something I have the knowledge about to check myself.

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[968workaholic]

The balance shaft gears are the same part number, that's why there are 2 grooves cut into them, so they can fit onto the upper or lower shaft and be timed properly. The 3k vibration does fit the indication of the shafts being out of time though. My quick check is to open the driver's door and hold the engine at 3k in neutral. If the door vibrates/shakes up and down, 98% of the time the balance shafts are out of time. Just my .02


A picture of the shafts with the covers off and the cam marks lined up would verify if they are oriented correctly

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[MCL968]

Don't forget, there is an inspection hole on the lower cover, so checking the shafts is relatively easy with a mirror. Remove the top shaft cover, put cyl 1 at TDC, check if the marks line up. usually it's just one tooth, and often it's the lower shaft.

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[Snufkin]

Thanks for the advice guys. I haven't actually run the car up to 3k at a standstill to see what the vibration is like, so I'll start with that. 

 

Checking the shafts would also be good. Doing anything beyond an oil change is new to me but I'm keen to learn. I've read through a lot of other posts about checking the balance alignment and I think it's slowing starting to make sense. Whether I can figure out what I'm doing when I actually look under the hood is another matter. But a fun job for the weekend.

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[WJH]

You can download the 968 manual and they have some good photos of balance

shaft alignment. I always tell my customers to look for the obvious first, then move

on to the more difficult.

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[Snufkin]

Quick update for anyone interested - the balance shaft alignment was fine, but my mechanic suggested it could be the wheel bearings... swapped them over and the acceleration is now so much smoother. For me the vibration was worst when the engine was under load at about 80kph. So worth keeping in mind for anyone else who gets a similar issue.

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