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Noisy clutch was NOT the release bearing in my '78
I had been saving to fix a noisy clutch pedal (see this thread if you care to) https://rennlist.com/forums/928-foru...ise-video.html With everyones help here, I had come to the conclusion that it was most likely the throw out bearing. This was not the case!
My mechanic says It ends up that the splines on the discs and stub shaft are all worn and stripped . What would cause this?
I mentioned to my mechanic that we will need the special Porsche high temp moly lube. He says he has never heard of using that stuff on the stub shaft and would only be putting some on the pilot bearing. This worries me. Is it possible that the lack of this HT moly has anything to do with this issue to begin with? I guess I don't really understand where this special grease goes and it's purpose. Can someone explain where it is to be used and its purpose?
I understand that I really should've taken it to someone that has specific knowledge and experience with the 928 clutch, but that is water under the bridge. please don't scold me for this. I just want to figure where to go from here.
For the record the previous owner had this clutch installed at Autobahn in Fairfax VA.
1) Is the whole reason for this failure the lack of this HT moly grease?
2) Any other WYAIT's other than the following?
Stub shaft
Dual discs
T/O and pilot bearing
Ball cup for the arm and the top of the torque tube.
Rear main seal looked good, but I will check it again.
Well, short version, the optimoly lubes the splines on the short shaft and clutch plates. Without it, the splines wear rather badly.
Roger carries it. You can simply ask for the "super duper special grease for the clutch" and he will know what you mean.
It gets put on the splines of the short shaft and the clutch plates (both is a bit of overkill, but that's ok). It's extra sticky so that it won't get flung off from centripetal force. It's suggested that a toothbrush be used when applying to make sure it gets into the grooves properly.
If your mechanic won't put it on, get a different mechanic (or at least tell him you want a warranty on the short shaft and the plates if he's not going to install them properly). The directions to lube the splines on the short shaft and plates is in the WSM.
If the splines are badly worn (and it looks like they are) then the discs and the short shaft need to be replaced.
I have brand new clutch shafts made from heat treated 300M to replace the more expensive stock shaft....
Extremely durable. Lifetime warranty (unless some idiot doesn't lubricate the splines....like what happened to you.)
$325
The correct lubricant is Porsche Extreme Pressure Grease. Lately, I've been sending my shafts pre-lubricated, with enough grease to lubricate the discs, T/O bearing, and pilot bearing.....saves $25 from buying an entire tube.
BTW....if your current mechanic is new to these dual disc 928 clutches, both you and he are in for one hell of an adventure. Do him a favor, get a copy of the clutch installation instructions from the Workshop Manual and tell him to follow them to the letter. That way he will only have to take it in and out a couple of times, to get it to work properly.
When you pick it up, start it up, push down on the clutch pedal, count to "2", and put it into reverse. If it grinds or is tough to engage....leave it for him to fix.
Do him a favor, get a copy of the clutch installation instructions from the Workshop Manual and tell him to follow them to the letter. That way he will only have to take it in and out a couple of times, to get it to work properly.
I've done hundreds of these things. I swear I've had the vast majority of them (until about 5 years ago) out twice.....minimum. I've had ones that won't release, removed the damn things, looked a second time (even more carefully...if that is possible), re-installed the same exact pieces the same exact way (or what I think is the same exact way), and had them work perfectly. I've had cars that I've done this 3-4 times....and then they suddenly work fine. I've tried the factory gaps on the intermediate plates, I've tried Kibort's gaps on the intermediate plate....no difference (unless the intermediate plate is very worn.)
And now that the "early" clutch discs are NLA and only the late clutch discs with the Marcel springs in them are the only thing available (they changed the intermediate plate when they made this change to compensate for the second Marcel)....the early clutches are especially "interesting".
I have found some tricks that the Workshop Manual does not mention...and my "success ratio" has gone from 50% to about 99%....but it has been a long, tough "learning curve."
Glad I'm not the only one. I've told every customer with a twin disk clutch that I expect to have it out at least twice, at a minimum, before they drive away. I think I've only had two that left here only being installed once and felt like I won the lottery. Had an '84 that I could never get it correct no matter what I did and asked the customer to drive it a few days. It self adjusted after a few days but felt bad about it. I had that damn thing out 4 times and wanted to burn it. Happened to also be one I put someones SC kit on.
Put the grease on it as the WSM states, there's a reason for it.
I've done hundreds of these things. I swear I've had the vast majority of them (until about 5 years ago) out twice.....minimum. I've had ones that won't release, removed the damn things, looked a second time (even more carefully...if that is possible), re-installed the same exact pieces the same exact way (or what I think is the same exact way), and had them work perfectly. I've had cars that I've done this 3-4 times....and then they suddenly work fine. I've tried the factory gaps on the intermediate plates, I've tried Kibort's gaps on the intermediate plate....no difference (unless the intermediate plate is very worn.)
And now that the "early" clutch discs are NLA and only the late clutch discs with the Marcel springs in them are the only thing available (they changed the intermediate plate when they made this change to compensate for the second Marcel)....the early clutches are especially "interesting".
I have found some tricks that the Workshop Manual does not mention...and my "success ratio" has gone from 50% to about 99%....but it has been a long, tough "learning curve."
Been there, done that - except for finding the 99% correct trick - I am still at random success - The Red 86.5 worked the first time.
I also did not know there were no more early disks. Is that 78-79?
Thank you all for your help. I have the WSM five CD set from Jim. I have not figured how to navigate around it. I will find it and print it out and give it to my mechanic. 928 International has a used one for $200. Is this okay to use, or do I need a new one of Gregs? I have his fuel lines and they are a work of art.
Greg did you say the early dual discs are NLA? what are my options if so?
Thank you all for your help. I have the WSM five CD set from Jim. I have not figured how to navigate around it. I will find it and print it out and give it to my mechanic. 928 International has a used one for $200. Is this okay to use, or do I need a new one of Gregs? I have his fuel lines and they are a work of art.
Greg did you say the early dual discs are NLA? what are my options if so?
If you can find a used clutch shaft without any wear on the splines, it will work fine. Tiny amounts of wear will "hang up" the clutch discs and not allow the discs to move freely (which they need to do to release.) Unfortunately, all of the orignal shafts are now at least 32 years old with many many miles. Good shafts are rare.....which is part of the reason I made mine. I also changed the design to help eliminate one of the big issues with assembly that the Workshop Manual ignores.
You have to buy the late discs....no choice.
The late discs don't work well with a brand new factory early intermediate plate.....there generally isn't enough "lift" in the "H" pieces to allow the Marcels in the clutch discs to unspring, without the disc dragging on the flywheel or the intermediate plate.
Fortunately, over the years, the "H" pieces wear and this generally provides enough additional clearance (using the early intermediate plate) to allow the front clutch disc to unspring and still not drag.
Glad I'm not the only one. I've told every customer with a twin disk clutch that I expect to have it out at least twice, at a minimum, before they drive away. I think I've only had two that left here only being installed once and felt like I won the lottery. Had an '84 that I could never get it correct no matter what I did and asked the customer to drive it a few days. It self adjusted after a few days but felt bad about it. I had that damn thing out 4 times and wanted to burn it. Happened to also be one I put someones SC kit on.
Put the grease on it as the WSM states, there's a reason for it.
At one point, years ago, I automatically doubled the labor for dual disc clutches, for this reason....and still lost money.
There were cars that I would have been farther ahead to hand the customer $500 when they walked in the door and had them take it to another shop.
I swear I considered finding metric "wing" bolts for a few of those cars....just to make getting the pressure plate off quicker!
If you can find a used clutch shaft without any wear on the splines, it will work fine. Tiny amounts of wear will "hang up" the clutch discs and not allow the discs to move freely (which they need to do to release.) Unfortunately, all of the orignal shafts are now at least 32 years old with many many miles. Good shafts are rare.....which is part of the reason I made mine. I also changed the design to help eliminate one of the big issues with assembly that the Workshop Manual ignores.
You have to buy the late discs....no choice.
The late discs don't work well with a brand new factory early intermediate plate.....there generally isn't enough "lift" in the "H" pieces to allow the Marcels in the clutch discs to unspring, without the disc dragging on the flywheel or the intermediate plate.
Fortunately, over the years, the "H" pieces wear and this generally provides enough additional clearance (using the early intermediate plate) to allow the front clutch disc to unspring and still not drag.
You should be fine.
Are the two "Late" discs I am looking for Sachs 200mm PN 928.116.011.35 for the forward one and .36 for the rear? or should I be using 928.116.011.23 and its rearward counter part?
When you pick it up, start it up, push down on the clutch pedal, count to "2", and put it into reverse. If it grinds or is tough to engage....leave it for him to fix.
I instinctively do this randomly at read lights with my 5-speeds, good to know as early as possible if the clutch is starting to hang up.
As I've said in many threads, if Porsche had gone with a traditional single disc clutch from day one, there would be far fewer 16V cars with syncro issues.
Originally Posted by GregBBRD
I've done hundreds of these things. I swear I've had the vast majority of them (until about 5 years ago) out twice.....minimum. I've had ones that won't release, removed the damn things, looked a second time (even more carefully...if that is possible), re-installed the same exact pieces the same exact way (or what I think is the same exact way), and had them work perfectly. I've had cars that I've done this 3-4 times....and then they suddenly work fine. I've tried the factory gaps on the intermediate plates, I've tried Kibort's gaps on the intermediate plate....no difference (unless the intermediate plate is very worn.)
And now that the "early" clutch discs are NLA and only the late clutch discs with the Marcel springs in them are the only thing available (they changed the intermediate plate when they made this change to compensate for the second Marcel)....the early clutches are especially "interesting".
I have found some tricks that the Workshop Manual does not mention...and my "success ratio" has gone from 50% to about 99%....but it has been a long, tough "learning curve."
.....and people questioned why in another thread I recommend anyone with a pre 85/86 version of this clutch facing a replacement, to junk the whole assembly and upgrade to a single disc.
If you are already facing $1,500 - $2,000 in parts, might as well go all the way and eliminate the weak point. This will pay off in dividends multiple times over down the road.
I love the DD clutch, great piece of engineering to have in a 70's designed street car, but it's overkill and unnecessarily complex.
I also cannot imagine trying to adjust one now without an inspection hole:
05-11-2017, 07:24 PM
Noisy clutch was NOT the release bearing in my '78
