90 ZR-1 #2273 - To be rescued

[S.hafsmo]

Expert opinion received from Bill Boudreau,

Hi Steffen,

The outer region of the clutch disc friction surface is considerably more worn compared to the inner, judging by the gassing groove depth tapering to outer . The gassing groove starts out even depth inner to outer when disc is new.

Good pictures by the way.

The pressure plate and flywheel I’ve seen look worse than yours and still operate just fine. Use maroon scotch-brite pads by hand only to remove surface glaze, replace the disc and install a fluted pilot bushing (GM P/N 10125896) inset 14 mm and absolutely do not apply grease in the pilot bushing. Doing so will cause the oil saturated pilot bushing to fail almost immediately. The throw-out bearing and pressure plate should be good for another 150K - 200K miles.

I have new Valeo solid hub clutch discs but they are too thick requiring 0.020” washers installed between the pressure plate and flywheel for compensation height to allow proper clutch modulation action. 0.320” disc thickness is ideal if you can find a new one at that thickness.