Clutch Chatter

[vandenham]

Hi,

I just finished installing a new clutch in my 78, and now it chatters (vibrates) when I start out.

I used emery (dry) on the flywheel and intermediate plates and was careful not to get any grease or oil on any of the plates. The yellow marks on the two clutch disks are offset to balance the weight properly. Once the clutch is engaged it works fine and does not slip like the old one did.

Is there something I should do to break in the new clutch disks to stop the vibration? Or is there something I needed to do but didn't during the installation that could cause this? I adjusted the intermediate plate back but maybe not well enough so it is offset and causing the vibration.

I am hoping I do not have to go back in there and redo the work (but I guess that is part of the do it yourself learning curve!)

Thanks,
Rick

[Normy]

"Is there something I should do to break in the new clutch disks to stop the vibration? Or is there something I needed to do but didn't during the installation that could cause this? I adjusted the intermediate plate back but maybe not well enough so it is offset and causing the vibration."

I don't know about the installation of the clutch, but if I were you I would go out and do a great big hairy burnout, and make sure you slip the daylights out of it while you do it. A good warmup might polish it off and make it more user friendly.

I changed my clutch at a shop in Orlando in 2003, and the shop owner allowed me to stand next to him while he did the work, so I saw how to do it. My clutch didn't chatter at all afterwards- in fact, it felt exactly the same, only it didn't slip any more. You might indeed have a problem. If the burnout idea doesn't work, contact a shop and ask for advice.

N!

PS: I just noticed that you are in Edmonton; I was there on April 29th. I work for an airline, and we stayed in downtown Edmonton at this hotel called "Sutton Place". It's a cool hotel, since it is linked via bridges to the mall in downtown. I was there in January too, and I actually wore shorts to go to the food court and then the gym in the place. YEG is a really pretty city- I walked down to the overlook just south of the hotel and you can see the river and hills beyond.

How the hell do you folks get up that steep road in the winter when it is icy?

[vandenham]

I reread the manual and think I must have the intermediate plate mis-aligned. I'll pull the pan off the bottom and check/adjust the alignment before I try to drive again.

Rick

(PS: Normy, in Edmonton they built a lot of indoor walkways because people buy more when they do not have to go outside to wander between stores. As far as the roads, the city spreads sand at intersections and on hills to help cars stop and go. People also put all-season tires on their cars because they have better grip on the ice and snow. It still is a challenge to drive!)

[ice-hot]

[QUOTE=vandenham;4658339]I reread the manual and think I must have the intermediate plate mis-aligned. I'll pull the pan off the bottom and check/adjust the alignment before I try to drive again.



Vandenham- most likely not the intermediate plate adjust. Did you have the flywheel resurfaced? Is the pressure plate new? Did you check the intermediate plate to see if it was true? (flat) Did you replace T/O bearing and guide tube?

Flywheels will bow from pressure plate, and intermediate plate will become waved from uneven disc wear. All will cause chatter.

I am doing a "79" US with 107K on car and all of above were bad. Flywheel intermediate and P/Plate.

I have pic's of all if they will help.

John

[vandenham]

John, thanks for the response.

I installed a new pressure plate and the two clutch disks. I didn't change out the others because those parts are so expensive. The old clutch was smooth and did not chatter, and when I took it apart the wear on the disks was very even. I should have checked to make sure everything was true, but just assumed they were because the old parts looked like they just had normal wear (not such a good idea in hindsight).

I am going to try re-aligning the intermediate plate first because I can do it easily without having to remove the whole clutch assembly. If that doesn't work, then I will pull it all out and get more new parts.

It will be a couple of weeks before I can do this because of other commitments I have - will report back here after I get in there and fix it up.

Rick

[Danglerb]

A tiny handful of people seem to be able to easily adjust the dual clutch. Many conjecture Porsche switched to the weaker single clutch due to the call backs at dealers for clutches issues.

I would put a few miles on the new clutch before getting too concerned.

[DPW928]

Pilot bearing?

[vandenham]

I just got back to working on my 78.

I pulled the transmission cover and adjusted the "H" connectors, put it back together and found it did not fix the chatter problem at all.

Then I pulled the complete clutch out again and looked at all the pieces. I found some marks (grease/oil?) on the pressure plate so think I must have got some on one of the clutch disks. I sprayed all the pieces with Brake Cleaner to try and de-grease the pieces and put it all back into the car.

This improved the driveablilty and it is now tolerable, but there is still some chatter. I feel like I am driving an old flathead Ford. I will drive it as it is for the next few months and if it does not clear up completely, I'll pull it apart one more time and see if there are more grease/oil marks. If so, I'll replace the offending clutch disk.

Got to move for now to fix other things like the air-conditioning.

Thanks for all your advice!

[lizard928s]

Vandenham,

I just posted up some info for others to see on the other forums.

You might like to read this.

However with your clutch chatter, before doing the sandpaper/light scuffing you really do need to get out a nice straight edge and verify that it is perfectly flat if it isnt then it needs to be resurfaced. I mean this on both the IP and the flywheel.

As well though the DD clutchs do not like to be slipped as much and prefer a much more agreesive launch than a single disc clutch. As well ensure tht all your bell housing bolts (4) are properly torqued down or you will get a very severe chatter. Also verify that your tranny mounts are in good order. But dont forget that it does take some normal rush hour city traffic to bed that new clutch in as well.

[Mrmerlin]

Did you make sure to align the discs the paint dots should be opposite each other on the shaft and the thinner disc ( hub / splined portion) is placed next to the flywheel.
Also did you use a new splined shaft and use the Hi temp grease?
Did you replace the release arm bushing?
Are the trans mounts good?
Others have reported trans mount replacement to cure the chatter. Though it would usually be while reversing

[vdubr928]

My experience is that is you don't resurface flywheel with new clutch it will ALWAYS chatter. Just my personal input.

[Danglerb]

Burns my biscuits to cut off bits of new expensive metal.

I've been reading this thread thinking about how to not surface my rusty flywheel. Something flat to sand it on maybe.

[vandenham]

Lizard - thanks for the link to the diagram of the H connectors. Wish I had seen this before trying to figure it out on my own. I believe my H connectors are adjusted correctly now. I put a steel straight edge on the flywheel and IP - they were flat.

Mrmerlin - I used the old shaft and didn't replace the release arm bushing. I put the yellow dots opposite, but your comment on the two clutch discs has me concerned. I got two clutch disks and they had two differing part numbers 928-116-011-23 and 928-116-011-24 but they seemed to be identical. I didn't measure the hubs/splines, but I think they were the same length. Maybe they sent me one of the wrong disks. Does anyone have pictures of the two clutch disks (1978)? Would there be a problem if I used two of the same disks?

I will check the transmission mounts as a good next step.

My plan is to drive it for a while as I am working on other things. Hopefully it will get better - if not, its back on the creeper - off with the headers and out with the clutch. It gets easier each time!

Rick

[vandenham]

The clutch chatter did not go away so I have pulled out the clutch again. This time I measured the flywheel and intermediate plate and you guys were all right - they need fixing.

Here are a couple of pictures of the intermediate plate and the thousands of an inch they are untrue.

Here is the flywheel side of the IP.



And the clutch side of the IP.




The flywheel is the same as the clutch side of the IP.

Can the IP be resurfaced or do I have to buy a new one?

Thanks Rick

[vandenham]

It is now one year later and I finally got the clutch chatter problem fixed. Thought it would be worth while to add a final note to this thread to help others that might have the same problem as I did.

Rather than buy all new parts, I thought I could just fix what I thought was worn out and everything would be well. Turns out I was completely wrong and should have just spent the money in the first place.

My clutch chatter finally went away when I replaced the throw-out bearing. The old one did not appear to be bad, but must have had enough play in it to cause the chattering. All in all, I installed the following new parts one step at a time and only got rid of the clutch chatter after the last step.

• two clutch disks
• pressure plate
• intermediate plate (and turned flywheel)
• throw-out bearing

Good thing I did not have to pay for the labour.

Rick

[jrenfrew]

Thanks for this great post Rick!

I've got a 78 car that I did a clutch on 200km or 6 years ago. The car has a mild clutch vibration when engaging the clutch gently at lower RPM. A more aggressive clutch engagement doesn't show the same symptom.

Its been so long since I did the clutch I can't recall if the bearing was also done. The "Porsche specialist" hack who put it in for me cross threaded the retaining bolts for the bearing and one bolt was only half inserted! Pulled it all apart myself after 50k of driving, found the mess and corrected the retaining bolts. It probably damaged the bearing now that I read your experience. I think I'll replace that bearing again and write back on my results.

Thanks!

[aluminum]

Those Black Spots on the I.P. are " heat spots " or some may call them Hot Spots or Evan other names. they look somewhat like water spots Also
Those Spots when they get hot well cause Chatter ! for sure . When they get hot and they well get hot they well expand and create High spots that hit the disk.
You can surface the plate but don't because the spots well come back . Replace the Plate and be done with it . Get a New one not rebuilt if your wise .
this place may not have a 928 Plate but if they do I doubt you can find a better place or part for the $
D & W Clutch & Brake
if they service your car I would buy a complete set . I would also consider to convert the Clutch to a single disk set up . But to each his own

[Danglerb]

Single plate, easier to adjust, not as good in all other respects.