A friction clutch pack exhibiting improved high speed stability includes a first plurality of friction plates or discs preferably having friction material on both faces interleaved with a second plurality of thicker reaction plates or discs. The friction plates comprise a formed core plate having multiple obliquely oriented or angularly offset sinusoidal waves. Male splines around the periphery of each friction plate engage complementary splines on a cylindrical housing. The reaction plates are flat and thicker than the friction plates and include female splines around an inner opening which engage complementary splines on a shaft or quill.