IDLER & BEARING AS 3990736 - Caterpillar

3408, 3412 Engines In All ApplicationsDescription of Change: New cylinder liners and O-ring seals are used in the above engines. The new liner has narrower and deeper seal grooves than the former liner, and the new seal has a larger inside diameter with a smaller cross-section diameter than the former seal. These changes lower the tension and the compression stress in the rubber when the seal is installed, and will extend the service life of the seal.Adaptable As: Direct replacement. The new 1W6280 Cylinder Liner is used in place of the former 7N943 Cylinder Liner, which is canceled, and the new 6V5121 O-Ring Seal is used in place of the former 2N6210 O-Ring Seal. It is not necessary to use the new parts together; the new liner and seal can each be used with the other former part in all earlier engines.