CIRCLE & BEAM AS 2594490 - Caterpillar

Family of Engines;
D11N, 776B Tractors;
777B, 785, 789 TrucksReference: Special Instruction, SMHS8508, "Special Handling Information and Installation Instructions For Crankshaft Seal Groups That Have Hydrodynamic Groves in the Sealing Lip.".Description of Change: The inside diameter of the wear sleeve, part of the crankshaft seal group, has been decreased by 0.05 mm (.002 in). This will provide a tighter press fit on the crankshaft. This change will help prevent movement of the sleeve on the crankshaft.Adaptable To: The part numbers of the 1W6974 and 1W6977 Crankshaft Seal Groups with the reduced inside diameter wear sleeve have not changed. The new seal groups can be identified by the "date code" for January 1, 1991 or later. The "date code" is stamped on the rim of the seal between the "CAT" trademark and the part number. In the date code system, the letters N, U, M, E, R, A, L, K, O, D stand for the numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 respectively. The date code will have six letters. The first two letter indicate the day; the second two indicate the month; and the last two letters indicate the last two digits of the year. For example, the date code " NUNUDU" stands for the date " 01/01/91.
The 1W6974 Crankshaft Seal Group (CW rotation) is for use in the front housing on SAE standard rotation engines and in the flywheel housing on SAE reverse rotation engines.
The 1W6977 Crankshaft Seal Group (CCW rotation) is for use in the flywheel housing on SAE standard rotation engines and in the front housing on SAE reverse rotation engines.