Ok I have been looking at clutches to install after I complete the Dr. Evil tranny rebuild. Won't bore you with the part numbers but in the 6 spring configuration I have noticed two different types of surfaces on the clutches. One completely smooth and a light cold

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And another much darker with groves

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Anyone have any ideas about what the differences are between the two? One better than the other?

The lower one is typical Sachs OE clutch. I've never seen or used the top one.

The top is more like the VW/Porsche clutch discs from the 60's and 70's. I had a NOS one somewhere.

The bottom one is a "modern day" clutch disc.

Ok I think I have this figured out. The first clutch is referred to as an "organic" material. And the second more modern version is a ceramic mix material.

Supposedly the organic material is better for standard driving and the others are a little more performances oriented.