Pressure plate wear., Causes. Options

[914Toy]

To the brain trust: re slight shudder when engaging the clutch in first gear to begin moving forward.

The clutch assembly is a Sachs brand 228 mm and was installed new about two years ago onto a new flywheel on my 2.7 911 engine, and now has some 5,000 street miles on it. Also new was the throw out bearing (Sachs) and nylon bush under the clutch fork.

I expected to see some clutch disk "burn" deposit on the fly wheel and/or pressure plate. To my surprise, while there were some small deposits on the flywheel and pressure plate, these parts and the clutch disk appear to be in near new condition - little measurable or obvious wear. However, the tips of the pressure plate "fingers (see pic) were worn down where the throw out bearing (TOB) contacts them. This suggests the TOB is slipping on the finger tips causing friction and wear. The TOB feels solid and spins freely like new.

I don't believe this is normal wear. Any thoughts/advice?

[TravisNeff]

I can't help with the reason for wear. I would make a crazy guess and say that maybe you have your clutch adjusted too tight. You should be able to pull your clutch pedal back by hand about 1/2 inch or so to know if you were in the ballpark. But if that was the case you would see evidence everywhere else with the flywheel getting hot and disk wear.

Honestly it doesn't look too bad. Except for the oddity of the 11 o'clock position, that looks like it is cut deep and the rest look a little more polished (maybe it is just the picture). Since it it always spinning you would think the wear would be the same across all fingers.

[914Toy]

I can't help with the reason for wear. I would make a crazy guess and say that maybe you have your clutch adjusted too tight. You should be able to pull your clutch pedal back by hand about 1/2 inch or so to know if you were in the ballpark. But if that was the case you would see evidence everywhere else with the flywheel getting hot and disk wear.

Honestly it doesn't look too bad. Except for the oddity of the 11 o'clock position, that looks like it is cut deep and the rest look a little more polished (maybe it is just the picture). Since it it always spinning you would think the wear would be the same across all fingers.

Thanks for your Quick response. I agree that I may have had the clutch too tight. You are correct re the uneven wear - slightly deeper at the 11 o'clock position . Perhaps due to slight differences in the original shape or spring strength of the fingers?

[TravisNeff]

I did a little digging.

https://forums.aussieveedubbers.com/viewtopic.php?tid=79304

Some suggest abnormal wear on fingers if the PP wasn't torqued evenly.

By any chance are you using ARP flywheel bolts and not using the 4mil spacing washer? ARP states not using any washers but I found out that you did indeed need it as the bolts will bottom out on the crank and the flywheel will be a little floppy. BTW there is a 3 mil and a 4 mil washer, from what I read you need the 4mm. That is assuming you are using a 901 flywheel, if using a 915 flywheel i think the 3mm is appropriate.

I did not use the spacer and read about it last week. I get to tear it apart and add it in, was able to find one on fleabay for $30

[SirAndy]

This is the part that the throwout bearing is riding on.

Do you like to sit at a stop while in gear with your foot on the clutch? Seems like there was a lot of contact between the bearing and the pressure plate.
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[Root_Werks]

This is the part that the throwout bearing is riding on.

Do you like to sit at a stop while in gear with your foot on the clutch? Seems like there was a lot of contact between the bearing and the pressure plate.
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I see that every once in a while. Most cars only take a few mm's before the T/O bearing will rest against the pressure plate.

Keep that foot off the pedal unless you're gonna use it.

[914Toy]

I did a little digging.

https://forums.aussieveedubbers.com/viewtopic.php?tid=79304

Some suggest abnormal wear on fingers if the PP wasn't torqued evenly.

By any chance are you using ARP flywheel bolts and not using the 4mil spacing washer? ARP states not using any washers but I found out that you did indeed need it as the bolts will bottom out on the crank and the flywheel will be a little floppy. BTW there is a 3 mil and a 4 mil washer, from what I read you need the 4mm. That is assuming you are using a 901 flywheel, if using a 915 flywheel i think the 3mm is appropriate.

I did not use the spacer and read about it last week. I get to tear it apart and add it in, was able to find one on fleabay for $30

Pic below shows the cleaned up fly wheel after using some fine emery cloth to rub off the small "hot spot" deposits on the fly wheel - now very close to new condition. The 6 flywheel bolts have: NBUS-XZN 140 stamped on them, and they have in-the-hole length of 26mm versus the total hole depth (flywheel plus crank) of 32mm, so they are not "bottoming out". To repeat this is a 2.7 911engine.

[dr914@autoatlanta.com]

clutch cable too tight

To the brain trust: re slight shudder when engaging the clutch in first gear to begin moving forward.

The clutch assembly is a Sachs brand 228 mm and was installed new about two years ago onto a new flywheel on my 2.7 911 engine, and now has some 5,000 street miles on it. Also new was the throw out bearing (Sachs) and nylon bush under the clutch fork.

I expected to see some clutch disk "burn" deposit on the fly wheel and/or pressure plate. To my surprise, while there were some small deposits on the flywheel and pressure plate, these parts and the clutch disk appear to be in near new condition - little measurable or obvious wear. However, the tips of the pressure plate "fingers (see pic) were worn down where the throw out bearing (TOB) contacts them. This suggests the TOB is slipping on the finger tips causing friction and wear. The TOB feels solid and spins freely like new.

I don't believe this is normal wear. Any thoughts/advice?

[TravisNeff]

OK, that is what I read elsewhere about bottoming out, I have a 2.7 too. Here is the washer/spacer I was talking about.

[porschetub]

Wow that wear looks more like wear after 50,000 miles,not sure if the pic makes it that way but the wear looks uneven which may suggest the p/plate is faulty ?.
Could be that some of the fingers are weak if the wear is indeed uneven as mentioned,reason for saying this is I had a 200mm T1 p/plate do the same thing.
I agree that a overly tight cable could cause this,is the pedal stop adjusted correctly ?,I found this a bit of a fiddle but ended putting it back where the original marks were in the wood floorboard.
Good luck.

[914Toy]

OK, that is what I read elsewhere about bottoming out, I have a 2.7 too. Here is the washer/spacer I was talking about.

The flywheel side facing the clutch disk has indents for the bolts - so no place for such a washer and in any case placing it there would not change the longitudinal distance from the crankshaft. So not the side for such a washer and also fo much more serious issues.

The flywheel side facing the crank shaft is shown in the pic below. I believe the indent for the crank shaft to fit in is exact and is critically required to center and align the flywheel to the crank. The indent is 4mm deep. So placing a 4mm or even a 3mm washer/spacer in there would be a serious mistake as centering and aligning the flywheel would be compromised. Perhaps you are thinking of the Type 1V set up?

[TravisNeff]

that distance washer goes on the outside of the flywheel, under the bolt heads.

[TravisNeff]

From porsche pet for 74-77 911

Also found the thread talking about the washer. https://www.early911sregistry.org/forums/sh...olts-901-vs-915

[914Toy]

From porsche pet for 74-77 911

Also found the thread talking about the washer. https://www.early911sregistry.org/forums/sh...olts-901-vs-915

The diagram is very helpful thanks. I read the ARP article and this is what I have. My bolts are 26 mm under the head with 21 mm of thread with 16 mm of this thread in the crank. I would need bolts 10 mm loner than the ones I have to have the same length of thread in the crank.

I am going to go with the cable adjustment being too short as the cause of the extraordinary wear on the pressure plate fingers. Hope I am right!
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[GregAmy]

That wear is between the pressure plate and the throwout bearing.

The throwout bearing is a bearing (duh) that has a surface that rotates with the pressure plate. There should be minimal relative movement between the two.

It appears like the part of the throwout bearing that interfaces with the pressure plate is not properly rotating; instead of rotating with the pressure plate it's wearing on the pressure plate.

Ergo...my call is "bad throwout bearing".

Contributing factor...bad flywheel pilot bearing, allowing the tansaxle input shaft to bind and/or move non-coaxially.

[914Toy]

That wear is between the pressure plate and the throwout bearing.

The throwout bearing is a bearing (duh) that has a surface that rotates with the pressure plate. There should be minimal relative movement between the two.

It appears like the part of the throwout bearing that interfaces with the pressure plate is not properly rotating; instead of rotating with the pressure plate it's wearing on the pressure plate.

Ergo...my call is "bad throwout bearing".

Contributing factor...bad flywheel pilot bearing, allowing the tansaxle input shaft to bind and/or move non-coaxially.

I agree with your analysis and forgot to mention that I am replacing the TOB even though i think the existing one is OK. Thanks for your advice.

[jcd914]

To me the un-even wear on the pressure plate fingers says, bad pressure plate.
All the fingers of the pressure plate should be under the same pressure and should wear evenly.

More wear on some fingers indicates more pressure of that finger.

When you bolt the clutch disc and pressure plate back on to the flywheel, check then relative position of the pressure plate fingers to each other.
They should be even so the TO bearing will press evenly.

Jim

[porschetub]

OK, that is what I read elsewhere about bottoming out, I have a 2.7 too. Here is the washer/spacer I was talking about.

The flywheel side facing the clutch disk has indents for the bolts - so no place for such a washer and in any case placing it there would not change the longitudinal distance from the crankshaft. So not the side for such a washer and also fo much more serious issues.

The flywheel side facing the crank shaft is shown in the pic below. I believe the indent for the crank shaft to fit in is exact and is critically required to center and align the flywheel to the crank. The indent is 4mm deep. So placing a 4mm or even a 3mm washer/spacer in there would be a serious mistake as centering and aligning the flywheel would be compromised. Perhaps you are thinking of the Type 1V set up?

No placement for that washer with recessed bolt holes...no way around that.

[sixnotfour]

Aftermarket Flywheel...... (IMG:style_emoticons/default/popcorn[1].gif)

[914Toy]

Thanks all. Hopefully a new TOB and pressure plate will solve this issue. Will post progress.