christiandk

Only one of my new plates has a mark....whats up with that!?

christiandk

Are these the right Sachs numbers for a 78?

Porsche number on one disc says 928 116 011 35 model year 80-86!?Sachs 1864 341 303

No porsche number on disc 2 Sachs 1864 342 203 009

christiandk

Looks like the old ones though. I just dont know if it will cause problems that only one disc is balanced. Maybe the one without mark did not need balancing. But that would leave me with one disc that has a heavy side and no disc to counterbalance!? Ohh the agony!

Dave928S

It's not all that difficult to sort them out if one doesn't have the mark.

Feed a piece of round rod or tube (or the stub shaft) through the centre of the one which has the mark, and then support on both sides on flat level surfaces by the rod. It should rotate and settle with the paint mark down, signifying the heavy point.

Do the same with the other disc, and mark the heavy point on that unmarked one.

When you install the discs you need to have the heavy points 180 degrees opposed, when mounted on the stub shaft, to achieve the best balance.

Because they are symmetrical they should be very close to perfect balance anyway ... this just ensures that you cancel out any very slight imbalance, and don't compound it.

christiandk

Genius Dave - thanks!

P.S. do you think I will be in balancing trouble regarding the PP and flywheel? Is it common to balance the parts individually or as a pack?

post 37

Thanks again.

https://rennlist.com/forums/928-foru...removal-3.html

Dave928S

I have the feeling that Porsche used to finally balance them as a pack, after they'd balanced the intermediate plate; as in my original (82) many balance drillings were in the pressure plate rim (which can't have been that far out), indicating to me that was the final pack balancing operation, after individual components.

When I faced the flywheel and the intermediate plate, and added a new PP, I wanted to keep the PP untouched so it could always be replaced without disturbing the balance too much (it was symmetrical/balanced out of the box). I bolted it all together and did the final balance drillings in the intermediate plate (where there was already one).

IMO it doesn't matter too much about balance of a single disc clutch (apart from race applications), where the PP and flywheel aren't likely to be out much as they are symmetrical and simple.

I think it can matter more on a double disc clutch, where you have the added IP with many parts ... which is why I balanced mine.

If you don't have many balance drillings on yours, it could be that you can move them around without any real problem ... but if it was me I'd get the balance right.

I know others here think it doesn't matter ... but I prefer to get things at least as good as factory, and preferably better where possible ... and it's a simple procedure.

christiandk

Thats awesome Dave. Thanks.

Usually I an bot this helpless. really

Looked at the old discs....identical ceners. One stamped 77 and one 78. The new ones are different. One has a longer hub/center that the other. I am getting pretty tired of this clutch job........

Dave928S

I feel your pain.

At first glance you appear to have the later revised discs, as described in the WSM Vol 2 - Read from Part 30.13. However ... one of them is NOT the correct number. Old were 23 and 24 ... revised were 27 and 28 or 33 and 34. The 35 you have does not appear to be correct, although perhaps it supersedes 34 ???. You need to get back to the vendor and get some clarification of part numbers before you put them in. Changes were made in 1980, to 'allow smoother engagement'.

The longer hub plate is fitted between the pressure plate and intermediate plate, and the shorter one between the IP and flywheel.

However .... to accommodate the revised plates, the guide tube was replaced with one 49mm instead of the original 50mm (easy to fix by just grinding the original down 1mm), but the stub shaft was replaced with one having a spline length of 56mm instead of the original 51mm (you can only replace the stub to remedy that).

The intermediate plate had alterations also to give a travel of 1.2 to 1.5mm of the adjusters (the old one was 0.7 to 1.0mm). Considering what we do to adjust these clutches manually, after install, I would doubt that difference would be a problem. I think the adjusters could be filed to give the extra bees dick of clearance anyway.

christiandk

Thanks Dave you have been a great help.

I have written Rosepassion in France and am waiting for their reply. Will get back when I have news.

Here are the discs I bought. On other European sites both discs look alike. But the pics here corresopnds to what I got but one disc is labelled 80-86.

http://www.rosepassion.com/en/cat/po...el/clutch/B116

Christian

So the seller told me the part is correct, but did not explain anything.

See post 8 here.

https://rennlist.com/forums/928-foru...ong-order.html

christiandk

So they insist it is correct and sent me the Sachs info. Looks like it is ok to replace one of the discs with the one with longer hub......

https://webcat-services.zf.com/index.asp?SPR=6

Dave928S

Yes ... they look correct for the amended versions, with the rear one having the longer hub. I don't think, from notes in the WSM, that you can even get the old plates, with the equal hubs. I was just concerned about the different part numbers from what I was getting in PET and the WSM, and thought you should get confirmation that they are indeed the right ones.

Note the small differences that they made (my post #8) to the guide tube, stub shaft and intermediate plate, and determine what you are going to do, in relation to those changes.

Edit: Just checked that Sachs info and pulled up the disc set that you have ... but it still doesn't explain the departure from the PET and WSM numbers, for these amended discs (one with longer hub). As I noted ... they look OK ... but they haven't explained the Porsche P/N difference.

christiandk

Dave I will try assembeling the pack tomorrow and see whats what.

The french vendors were pretty rude in their reply. Probably last time I take my business there.

I thought that maybe the US and Row had different discs since the Sach page says "not valid for US, CAD, Mex etc." Mine is a US car.

Again I really appreciate your help.

Dave928S

Here's what I'd do ....

1. No matter what, you should take 1mm off the nose of the guide tube, as you have the thicker amended assembly to release.

2. For it to operate really well, you should have a new stub shaft to give full spline engagement for the longer combined length of the two hubs. You might not get the full benefit using your old shaft.

3. You should check the clearance you have on the H adjusters as per the WSM, and increase clearance a bit if needed.

All easy to do now, but a total PITA if you have to pull out to do later ... and all necessary for the amended discs, which are all you can get now.

christiandk

Why would you want to shorten the Guide just 1 mm.

The base of the hub on the new rearward disc is the same length as the original is overall. The extra length on the new disc is smaller in diameter than the base and it sort of fits nicely in the back of the TOB.

Wil post pics when all is together.

Dave928S

I know it seems strange to only take off 1mm, but it's what they state you need to do in the WSM, under that section I posted earlier (WSM Vol 2 - Read from Part 30.13). Read through it and it will answer a lot of your questions as to what the changes were, and why new amended parts are required.

The new tube is 49mm and the old is 50mm, and they say to grind 1mm off the old one if using new/revised discs. My guess is to give/restore the correct working clearance to the TOB. It's not only the hub which is different, but the liners which have different/thicker spring plates between them.

I have no idea what will happen if you leave it at 50mm, or not adopt the other changes ... but there must be reasons they specified these things ... and went to the expense of making amended parts. They also specifically state to not mix new and old parts.