A method and a sealing system for sealing the space between a piston and the hub of a torque converter lockup clutch is provided. According to the method and the sealing system, the seal is pretensioned with its cylindrical surface facing the piston bore. In an embodiment of the invention, the first seal is fastened by a second seal. The invention allows minimization of oil leakage flow and at the same time to linearize its dependency on the differential pressure. Spontaneous sealing may be reduced, thereby directly correlating the contact pressure of the piston—and thus the torque of the torque converter lockup clutch—with differential pressure and eventually allowing for smoother travel.