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?

Click to view attachment

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?

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

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.

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.

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.


Click to view attachment

clutch cable too tight

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.

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.

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?

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

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!

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.

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

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

Aftermarket Flywheel......

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

Make sure you have a 1/2" free play at the pedal. I use a ruler or tape measure and pull and push the pedal by hand to measure it.

Another consideration is that the throwout bearing and pressure plate were somehow not co-axial. I'm sure you can imagine that kind of wear if one was slightly off and they were rotating on slightly-different centerlines.

I believe above you mentioned you're replacing the plastic fork bushings and pivot cup? Also check the condition of the tube that the TOB slides on, to ensure no excessive wear, and make sure it's centered. Probably want to replace the trans input shaft seal anyway...?

There is also the shim behind the ball for the cup bushing on the throw out lever. When people resurface flywheels they may add more washers. I am not sure what thickness, if any washers are needed. Something to look at or think about before you put it back together.

Shudder at take off ?
Possible bent throw-out fork or uneven wear where lugs of TOB fit into fork.
TOB also needs to rotate freely on axis of lugs
As mentioned incorrect clutch adjustment.....no free play

This is one you should check especially if you have a heavier than stock PP. I welded in some gussets on my shaft arms (forks) because I have a HD PP on my 3.0 /6 conversion.
HD RB shafts and/or welding up the forks are common in the type one trans crowd.

Mark...got a photo of the gusset weld-up??

Sorry not of my cross shaft but this ebay ad shows the bugpack type 1. Mine looked similar once done.

https://www.ebay.com/itm/EMPI-BUGPACK-18-10...2-/264129462098

What does the wear on the TO bearing look like? If the PP was wearing then the TO should show a similar profile.

Usually it's not so much what it looks like but what it sounds like.
The typical failure of a TOB is noise that changes with pressure on/off the
pedal. This is caused by dried out lubrication wihin the bearing.
Less common but possible is the TOB sticking or resisting free motion in the fork.
Another issue is the TOB sticking on the guide tube......last but not least is
a worn out pilot bearing.

The throw out bearing (TOB) looks perfected at first glance, and has a smooth no slop action and turns easily. There is some slight wear evidenced by a bur around the outside of the contact ring, and in certain light shining back to ones eye there are some very shallow "indenture scallops" on the contact ring surface. There were no typical TOB sounds before removing this TOB and no vibration or sound when spinning it in my hand. It is not dry, but possibly the grease was beginning to dry. The fork is in good shape and the plastic positioning shims/spacers are in good shape, and the plastic ball cup was new and looks perfect. The TOB tube looks OK as does the needle pilot bearing which still has grease.
Bottom line, the TOB appears close to good condition as does the guide tube, clutch fork, and spacers, and ball white plastic cup. But I will be installing a new TOB, along with a new pressure plate assembly.

Looks typical of clutch cable too tight.

Completed installing the tranny with new pressure plate (Sachs 228 mm) on the aftermarket flywheel - cleaned up with some fine emery paper - and a new throwout bearing. Adjusted the cable so that the clutch engages at about 1/3 to 1/2 distance out from floor board stop. Clutch engages perfectly and sooner than I remember the previous set up. So cause of premature wear and shudder appears to clearly be due to having had the clutch cable too tight. Lesson learned

"Adjusted the cable so that the clutch engages at about 1/3 to 1/2 distance out from floor board stop"

.....proper clutch adjustment is not determined by where you feel engagement.
It is determined by free play at first pedal motion....at the top.