The problem with replacing only the clutch disc is the fact that the surfaces of both the flywheel and the pressure plate have probably become highly polished, or possibly even glazed from years of slipping a little every time you get into motion from a standing stop, or slip the clutch a little while backing up. The new disc will have a difficult time getting a good grip on those slick surfaces. Part of the rebuilding process on a pressure plate is regrinding the friction surface to the correct finish, one that allows the disc to grab properly. For best results, the flywheel also needs to be removed and reground. Replacing just the disc is sort of a "shade tree" fix- - - -better than nothing, but it will seldom give a really good or long-lasting improvement in performance.
Jerry
