Current seals feature a lay down sealing lip of low-friction PTFE with unidirectional spiral pumping grooves. An outer dust-exclusion lip keeps airborne dirt away from the primary sealing lip. The sealing lip does not touch the crankshaft, because an integral wear sleeve provides the running surface and protects the lip during installation. A separate replacement wear sleeve is not needed. The wear sleeve and outer carrier are joined together, forming a unitized seal assembly.
Because of the spiral grooves on the sealing lip, a front crankshaft seal will leak if installed at the rear, and a rear crankshaft seal will leak if installed at the front.
Wet-flywheel-housing applications require a double-lip rear seal to prevent transmission oil from migrating into the engine. This seal is similar to the single lip seals except for the extra lip, and the wear sleeve and outer carrier are not joined together.