Friends,

Ever since finishing a clutch job I have experienced clutch chatter when taking off from a stop or in slow traffic where I need to feather the clutch in and out. The clutch neither slips nor drags, it just doesn't engage smoothly. I have removed the pressure plate and clutch disc and found no signs of contamination or weird wear. The machining marks on the flywheel are still visible. I had the flywheel resurfaced and the pressure plate and flywheel balanced. The clutch has about 12,000 miles on it. It is a "Power Friction" kit from Vertex Auto.

I've uploaded pictures of the flywheel, friction disc, pressure plate, guide tube and input shaft splines. Any suggestions would be helpful.

 

Anyone?

Also, I have stripped out 4 of the 9 triple-square pressure plate bolts. After drilling off the heads to remove them I have to ask myself if any grade 8 allen head bolt of the right size could replace them or should I buy new triple-square official Porsche ones and risk stripping them out when torqueing them down.

Also, can I replace the two bolts that clamp the torque-tube shaft to the transmission input shaft together with more generic grade 8 allen bolts or should I look for special Porsche bolts?

I will appreciate any advice...

Perry

 

I recommend that you use the proper triple square bolts; be sure to tighten them in a cross-pattern to create equal pressure prior to torqueing them. I've purchased those bolts from 944online in the past.

 

Yes, I agree. I will purchase the correct bolts. I was just wondering if anyone has used a generic bolt in this application. I always torque down the pressure plate bolts evenly in a cross pattern.

Does anyone else have a problem with clutch chatter? Should I set up a dial indicator to check for run-out on the flywheel face? Does the face of the flywheel look normal?

 

Here are some general thoughts / opinions on these driveline questions:
The performance / smoothness of an aftermarket clutch will always be questionable compared to that of the original equipment. Original clutch discs cannot be installed backward but worth checking that an aftermarket disc is installed facing correctly.
The blanchard grinding marks on the flywheel appear to be a bit course and uneven, there is also evidence of previous overheating damage. The high spots created by overheating are usually not remedied by surface refinishing and will return with use.
The type of grease used on the driveshaft splines and guide sleeve is important to smooth operation. Porsche offers the correct and recommended grease if in doubt.
Grade 8 designation applies to SAE and not metric fasteners.
Clutch pressure plate socket head cap screws are grade 8.8 and are available from www.belmetric.com
Driveshaft coupling fasteners are highly stressed and should be sourced from Porsche.

 

I can't add much but that guide tube is NOT looking great. They're inexpensive and, so long as you're in there, easy to replace.

I've never had a flywheel resurfaced so I defer to Gage's experience but, have you looked at some of the other components, as well, to make sure they're OK? I'm thinking of the pilot bearing in particular. It's a little bit of a pain to get out but, at the very least, you have clear access right now to inspect it.

The other thing that may be happening could be non-clutch related (big, big maybe): torque tube bearings. Probably not what's going on as I think they present differently when they start to go but maybe you can listen to them spin and get an idea if they're acting up.

Let's see what else: how is the transmission suspension?

Good luck

 

Thanks for the replies.

I have a new guide tube. I will use Porsche bolts for both the pressure plate and the driveshaft coupling. Thanks for the SAE/Metric differentiation information for grade 8/8.8 bolts.

The previous clutch (which I believe was the original one) did not chatter. I had the flywheel resurfaced as a precautionary measure. Gage says that there are overheating spots on the flywheel. Can you describe them? What should I be looking for?

I have a tube of Sach's brand spline grease from a clutch job I did on a 911.

I have also replaced the motor mounts (genuine Porsche) recently and also replaced the transmission mount about 6 years ago. I am doing all this work now because I have completed a transaxle rebuild to quiet a noisy differential. I have also replaced the torque tube bearings with Black Sea super bearings.

Has anyone had to check the runout on a flywheel?

 

The hotspots on a flywheel will show up as discolorations. In your pictures, I think what @Gage is referring to are the blue spots/blotches that can be seen. It may be an artifact of the pictures; you'll be a better judge.

I've never measured runout on a flywheel, sorry. The closest thing I can give to (maybe) help is that over on the 928 board there should be some posts on measuring runout in that area for thrust bearing failure. That problem occurs on the automatics but the procedure (which I've only ever just observed, not performed myself, so I have no real details) should be applicable.

Good luck

 

I agree with Gage on the machine work it looks rough. Im not real particular OE verses Aftermarket but some times it comes into play. At close to 600 bucks according to Vertex site thats not cheap. Can you actually place the disc on the flywheel either way [both sides] if so then I would want more specific instructions from the manufacturer. Vertex says its their own design if you will, it might be worth a phone call. If not then its pretty straight forward. I agree the tube looks beat up. Considering where you are located Ill assume you dont have any fastener specific stores in the area maybe? With that said ya go back with the triple square but I would have a problem with a hex as long as your tools are of decent quality and more importantly grade! Heres a link I found with a very quick search I would assume they know what they are talking about.
https://www.fastenermart.com/underst...d-classes.html

I have removed a few clutchs in my time and flywheels on euro imports at a min and best of my memory 10.9 used and a fair amount of 12.9 I personally would use 12.9 and make sure all the threads are really clean.
Final note I would go ask the Vertex guys a ? or 2 and have the flywheel looked at again. As mentioned above your location correct me if Im wrong probably does not have a lot of places for machine work Etc. If you feel you need to travel a bit and found another machine shop then do it. Watch a couple videos online and see what they do. Do your best to compare the finished product on the video and what yours looked like. Food for thought!!

One more note tool wise allen or any kind a female type head needs to be clean so the tool is set to depth. Tool quality is important but you dont have to walk onto a Snap Off truck to find it. If I find a stubborn socket type fastener thats a little sloppy Ill use some valve grind compound as a filler. Dip the tool into the compound [just a small amount] and then tap it into the bolt or what ever with a hammer and seat it. The material help fill the gaps.

 

Gasngo,

Thanks for the response.

I do live in a remote rural area. The machine shop that did the work is 75 miles from my house. I am not too familiar with what finish is normal on a resurfaced flywheel. When I got it back from the shop it looked clean and resurfaced so I put it back in. There are no local mechanics that I would trust with working on my Porsche so I always do almost all of my own work (that goes for my dd Subarus, too).

The fiction disc is asymetrical and can only go on one way or it would get jammed into the pilot shaft bearing.

I do have a quality triple-square driver for the flywheel bolts as well as the pressure plate bolts. I just need to be more careful next time.

I am going to order new fasteners from a Porsche dealer or from Pelican, etc., clean all the surfaces, then measure run-out.

 

Got to love the Subarus. My aunt & uncle lived in Durango part time and near me here in Tex and drove Subs. They are gone now but my cousin live in Bayfield and drives one. He just got one recently always had jeeps. He too has a condo near here when he showed up the other day I just looked and thought of the Dr Rick progressive Com. I would still call Vertex for some feed back. Now whether they have anybody that really knows anything is another story. Its been a while since I have had to work with something like that but the machined surface just seems to be off. If the motor is spinning clockwise I would like to think I would see the swirls the opposite direction. I might be grasping here but justs get my attention more than anything out of the whole deal. Take your time check and double check. Some of the videos I saw where informative I say watch a few. If anything pops up Ill chime in.