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Clutch Alignment

September 26, 2010 | Troubleshooting & Repair

Text and photo by Ab Tiedemann

I have taken the clutch alignment task one step beyond the shortened input main shaft tool that some use. Below is a picture of my set-up which shows the extra two aids used to center a Kennedy pressure plate and the main shaft for the disc when installing the clutch cover on a 200 mm assembly. The "extra aids" are fashioned similar to the 911 tool, but have the interface for the 356. These aids are in production. Look for an announcement on 356Talk when they are ready.

There is no "Factory tool" listed for this procedure. It is one of common sense or at least one that has logic for the mechanically apt. When the 911 was introduced, the clutch plate was initially centered with removable loose pins [referred to in the 911 Worshop Manual as "dowels"]. See illustration III.245 of Section 52E in the 911 Workshop Manual. [Click here for a PDF scan of that page in the manual] The Factory tool number for this task sequence is unknown to me, but I have three (3) like those in the illustration previously mentioned.

The 356 flywheel has 2 holes for initial alignment of the clutch plate. There are corresponding holes in the pressure plate. However, these holes may be and are most often ignored when installing the pressure plate [even by the "professionals"], since it has no favored orientation unless it has been "clocked and pinned" at a machine shop. When balanced and marked in the pinned position, it assures that it goes on back the way it was balanced with the flywheel as this is the most convenient mounting surface for the pressure plate for this operation.

You cannot use two of the three 911 P(?) tools for the 356 application because the dowel pin size is different; 6mm for the 911 and 5 mm for the 356. The two pins shown in the photo above are custom manufactured for the 356 application using the 911 P(?) tool for proportions. Step 7 shown in the PDF file should never be avoided and it is important to use the correct grease that is suggested. I have had a 1 lb can of the graphite grease mentioned since 1960. I only use it for this application and I am a long way from the bottom of the can.

A shortened 356 transmission main shaft [mentioned on step 8 of the PDF file] interfaces with the splines on the clutch disc perfectly and the journal of the main shaft fits well with the bushing in the flywheel gland nut to assure concentricity of the gland nut bushing and the splines when the engine is installed. It is a set-up that precludes the expense of pinning the pressure plate [if the tools shown are used] although many would argue, convincingly, that all that is not necessary. And perhaps so—until you are the person that is the recipient of a task completed with makeshift tools like broom handles and turned down wood dowels or the held end of a ratchet!

Positioning the clutch plate with the custom fabricated tools assures that the pressure plate always returns to the proper orientation and is concentric within the true position tolerance of the mating dowel pin holes with respect to the pitch diameter of the gland nut mating threads. [tersely said in step 9 of the PDF file without explanation] It is just another way to eliminate variables in an expensive assembly. Don't forget to use 8.8 [old 8G] or 10.9 [old 10K] fasteners with locking elements as stipulated in Step 10 on the attachment. I am certain that 10.9 fasteners were used on 912 application and 356SC as well. Earlier cars used the metric 8.8 grade. The stronger fastener [10.9] can be used for all 356 and I recommend it. The load on the 180 mm clutch pressure plate fasteners is higher for a given torque transmitted, but 8.8 was plenty good enough for an unmodified 1600 Super [now putting out about 160 HP at the track with legal modification and aircraft fuel].