Patrick L

I think I'm having bad lucks.....
Just solving my tranny slave cylinder issue (finally found the part number of rubber bellows), I found another more serious issue on the clutch.
During my engine rebuild, I installed a set of light weight flywheel and new Sachs clutch kit (modified by SPEC). The engine runs fine, however, when my technician tried to move the car in the garage the first time after rebuild, at very low speed, the clutch is slipping!
According to my technician, he thinks that I might get the wrong parts and the clutch or flywheel seems too thick which cause the slip. I purchased the lit form a reputable shop in US and the seller confirmed that the kit he sold me is the correct one for 964.
Anyone know how to check if the LWF/clutch set is for 964? (part # or something on the clutch?) Is there any potential issue that will cause the slipping? (wrong installation, faulty master cylinder, etc.?)
Attached are pictures of the setup.

JasonAndreas

How thick is the flywheel and who makes it? Its tough to tell from the photo but it doesn't look to be the same size as the Porsche factory LWF? What is the Sachs part number on the release bearing? The arms are nearly 0.5" shorter on the stock release bearing so a mixup there could also slip the clutch. The slave cylinder can also be at fault but your mechanic has probably checked that. Do you have the part numbers for everything? (flywheel, release bearing, pressure plate bolts (or their length)

Andy Roe

Just happened to have an LUK flywheel lying around...width 2" or 50mm.

chris walrod

One comment I have to offer, which is prolly not your problem, the Sachs disks for LWF kits are labelled wrong. Gearbox side is actually engine side. This recently happpened to a buddy of mine while installing a LWF kit on his 993, which carries 964 p/n's. Pretty sure its the same disk, which also has a 996 GT3 application. FWIW..

Patrick L

Chris,

Thanks! The seller told me the same thing that my disk might installed the wrong side. My technician tols me he tried both sides when installing it, and found only one side will fit. sO he thinks it should be installed at the right side.

There is one thing he just told me. When he installed teh clutch, he can't reuse the original clutch bolt which appeared to short (around 10mm short), and he bought some longer bolts. As I know those bolts can be reused. Is there anything wrong with this? Is it the wrong clutch size? (is it possible I got the 3.2 clutch or something else?)

Thanks!

Eric Kessel

When I put my disk in the wrong way, once the car started there were sparks shooting out the bottom access hole of the transmission...... and a hellish squeal.... the guide tube was being machined by the clutch center....... if it's in backwards, you really can't miss it once the car is started.........

Patrick L

Is everyone using the original guide tube for LWF? Or I should use the RS one? (seems they are different)

chris walrod

Guide tubes for the LWF should be longer than that of DMF. Sadly, I cannot remember exactly how much longer.

Your wrench telling you he had to substitute, I presume, the pressure plate bolts for longer one, makes me a little nervous. The PP bolts will seem short, but end-up working as designed. Wonder if these longer bolts have bottomed on their non-threaded (shank) portion of the bolt and not clamping-down enough on the disk?

I know for a 993, a clutch disk in backwards didnt present any evidence of such mis-installation. Car ran fine with no noises or other. It just wouldnt release.

The splined hub is offset, and should face the flywheel, irregardless of how its labelled. The reason this particular 993's clutch wouldnt was due to this splined hub just barely making contact with the guide tube. But, not enough to produce sparks and noise..

Hope this helps!!

Eric Kessel

For my 90 C2 with the LWF, i'm using the RS guide tube # 950.116.813.30

When I upgraded to the Andial Mid-Weight flywheel, I did have to replace 3 of the pressure plate bolts with longer bolts (45mm standard, and 60mm for the weight Andial put on)

JasonAndreas

The stock bolts are M8 x 40 and for the LWF you need M8 x 45.

Eric,
I wonder if this was the reason you were able to bolt the clutch disc on wrong? When you walked me through my first (of several ) clutch jobs I tried to follow the instructions from Sachs for orientating the disc and there was absolutely no way I could bolt the pressure plate down the wrong way because the bolts were just too short. I ended up calling Viperbob at 11pm on a friday night and for some reason he picked up right then and set me straight.

JasonAndreas

Pat,
Is your lightweight flywheel an OE Porsche version or aftermarket (it looks aftermarket)? What is the part number for your release bearing? In the photo below the release bearing on the left is the RS version (Porsche #944-116-080-01 Sachs #3151-227-001) and the one on the right is Porsche #950-116-080-08. Your flywheel looks to be the same size as a dual-mass which is not the case for the OE LWF so if you are using the wrong release bearing the disc will slip.

Eric Kessel

Jason,
My biggest problem was that I didn't pay attention when I took the clutch assembly apart. The car already had the LWF installed. I pulled it apart to send to Andial, since the stalling was unbearable..... Andial drilled out three of the threaded holes in the flywheel, so you had to bolt "through" the flywheel, into the weight they mounted on the back (engine side). I don't believe it changed the positioning...... I just put the clutch in backwards....... The second engine drop was much quicker than the first.......

JasonAndreas

I noticed the same thing.

Patrick L

Jason,

The flywheel is aftermarket. How do I know which release bearing I should use? I will take the tranny off and check for that.

Thanks!

Patrick

JasonAndreas

If everything is still attached and your car is on a lift you can check the release bearing, slave cylinder, etc. by looking through the 3 openings on the transmission bellhousing.

There are two openings on the side and one on the bottom:


remove the rubber shroud

also


I don't have an image taken from below. You should be able to tell if the pressure plate is bolted down properly or if release bearing is disengaging the clutch or if the slave cylinder is sticking, etc.