Clutch questions

[ohecht]

I put in a new Sachs Powerclutch 3k miles ago, and it is totally slipping. Here are some facts and a few questions:

- The slipping only happened on 3rd or 4th at above 4000 rpms Saturday, but was almost everywhere in the gears and rev range Sunday, unless I was extremely gentle on the accelerator. That seems to be a very fast wear rate.

- There are no leaks from the bellhousing to indicate any type of oil contamination.

- I think I had the TO arm "pre-loaded" for the first 2k miles, due to a cable adjustment error. I think this may have accelerated the clutch wear, but I am not sure how that is possible, since the clutch never slipped once (not even a little) during that period. I don't see how that could cause accelerated wear if it was clamped enough to hold power all that time. Could it even wear out that fast?

- Adjusting it properly once it did start to slip got me another 1000 miles with no slipping, no matter how hard I stomped it.

- Is the disk the only real possibility, or could the flywheel have been overmachined? I am trying to gather parts before I pull the engine again, but I don't want to buy parts I don't need.

- Does it make sense to have the disk be relined if that is the problem? I would think everything else would be fine after only 3k miles.

- Any other good disks besides Sachs that come as a disk only? I am not wild about putting a duplicate clutch in there after seeing this rapid wear, even if it was accelerated by a poor adjustment.

Thanks in advance.

Olivier

[johnsjmc]

I just dealt with a similar situation although not a Porsche or a Sachs clutch. The new clutch seemed to be worn out in a 10 day period during which time the cable clearance went away .We initially blamed the cable preload and an insensitive driver until we took it apart The friction surface had separated from one side of the disc It was completely replaced under warranty. Unfortunatly we had to warranty the labour The sachs clutch is a good product I would wait to see the cause before ordering parts.

[ohecht]

I will definitely look for something similar. The preloading seems like an obvious cause, but, the more I think about it, the harder it is to believe, since there was no slipping during those 2000 miles that would have actually accelerated the wear.

Thanks,

Olivier

[ohecht]

Here are some pictures... the disk originally had slots in it ("power" clutch), but they are long gone. Remaining thickness is .231".

The worst part is the flywheel and pressure plate...they both look like they have massive heat marks, and the flywheel seems scored wear the disk was spinning.







Can all this happen from a poorly adjusted clutch even if it never slipped until right before I took it all apart again? The machine shop had trouble measuring the remaining thickness of the flywheel and I had them redo the inside edge to make sure it was square. Could overmachining the flywheel cause this?

I am pissed at myself that it looks like I need a whole new assembly and flywheel after 3000 miles!

John, is this what would happen with a friction surface defect?

Anyone have a recommendation on a street clutch that will hold more horsepower?

Olivier

[johnsjmc]

That disc probably is the more recent style power clutch without the slots. If there is any material standing above the rivets then the disc isn't worn out. There is considerable heat damage to the pressure plate and the flywheel The flywheel surface appears to have small surface cracks visable (like 50000 miles worth) I expect the cluth was slipping all along perhaps from maladjustment or feathering the clutch for a drag race start. Do you have a 3.6 installed? A normal 3.0 or even 3.2 gets in excess of 50000 miles of normal use from the stock clutch(also made by sachs) The power clutch should get more

[Neilk]

Olivier,

I can't really answer your question, but I brought my used flywheel to a well known shop in the Dallas area to have it inspected. They said that my flywheel would end up close to the wear limits after machining. They also mentioned that when you get close to the limits, the geometry of all the assemblies isn't quite correct and you can have some problems. Perhaps, you were too close to those limits.

Lastly, I am just repeating what I remember hearing. Perhaps they said something different that I misunderstood.

[David]

That's the worst clutch I've ever seen. I can't imagine how all that damage occured in a few miles. I wouldn't reuse that flywheel with all the cracks in it.

[Nitrometano]

Send the pressure plate and the flywheel to a machine shop to doing a re-surface job. In the pressure plate the same thickness that was removed you also will need to remove the same thickness around the pressure plate, where the bolts come thru. This will work.

[ohecht]

It was a power clutch, and it did have the slots in the material. I know because I got the non-slotted disk twice before I finally got the right part.

I will definitely replace the flywheel, and probably just start over with a new disk and PP. I don't want to take any chances this time with machining the parts, it is worth the piece of mind to have all new parts and a good baseline starting point. Maybe I can have the disk relined someday when I need some exotic material or something to hold more power.

It is amazing that this could occur in 3000 miles with no noticeable slipping. I never abuse the car at all on the starts. I do get on the gas hard above about 3500 rpms and wind it out to 6000 or so occasionally, but nothing involving any clutch movement.

There was no noticeable slipping until the last 100 or so miles. I think what may have happened is the machine shop that did the flywheel did not get a perfectly square "inside edge" on the corner of the raised outer edge (why is that edge there, anyway?). I even took it back to them before installing it because I was worried about it, and they may have made it worse by over-machining it then.

I hate re-doing work and re-ordering parts that should have lasted at least 50k miles so soon!

Olivier