BOLT 8T7930 - Caterpillar

3508 (68Z),
3512 (65Z),
3516 (71Z) Industrial;
3508 (69Z),
3512 (66Z),
3516 (72Z) Marine;
3508 (70Z),
3512 (67Z),
3516 (73Z) Generator Set;
G3508 (4WD, 2JF, 9TG),
G3512 (4KC, 5JD, 7NJ),
G3516 (3RC, 8LD, 4EK) EnginesSUPPLEMENT: 04/01/97Engine News,, January 1997, Page 8, "New Idler Gear Assembly Containing Larger And Stronger Bearing Is Less Prone To Cavitation Erosion".The serial numbers appearing on Chart 2,, Page 10, with respect to the "Gas" application refer ONLY to the 8N-5745, 1W-9553, and 8N-5678 Accessory Drive Groups mentioned in Chart 1, Page 8.
The serial numbers appearing on Chart 2, Page 10, with respect to the "Generator Set", "Industrial", and "Marine" applications refer ONLY to the 8N-5769 Front Gear Group mentioned in Chart 1, Page 8.
The serial numbers that apper on Chart 2, Page 10, DO NOT refer to the 8N-5620 Front Gear Group. This Supplement will provide the neccessary serial numbers that were absent from Chart 2.
The former 8N-5620 Front Gear Group has been replaced by the new 122-9281 Front Gear Group. The serial numbers on the following Chart 3 refer ONLY to the new 122-9281 Front Gear Group.
Reference: Engine News,, May 1995, Page 1, "New Front Gear Groups Includes New Gear Assembly With New Stronger Bearing".--------------- END SUPPLEMENT ---------------Description of Change: A new idler gear assembly, containing a larger and stronger bearing, has replaced the former idler gear assembly used in the above (slow speed) engines. The new idler gear assembly has a smaller finished diameter than the former assembly. The new bearing is manufactured with a higher fatigue strength material and a larger outer diameter than the former bearing.Adaptable To: The new 116-3242 Idler Gear Assembly directly replaces former 2W-7321 Idler Gear Assembly in the gear groups shown in Chart 1. The new 116-1365 Bearing, contained within 116-3242 Idler Gear Assembly, directly replaces former 8N-5301 Bearing, contained within former 2W-7321 Idler Gear Assembly.
The new 116-3242 Idler Gear Assembly has a finished diameter of 105.97 0.01 mm (4.1720 0.0004 in) which is slightly smaller than the 106.000 0.065 mm (4.1732 0.0026 in) finished diameter of former 2W-7321 Idler Gear Assembly. (Refer to Illustration 1.)
The higher fatigue strength of the bearing and the smaller clearance between the idler gear assembly and bearing reduces the potential of cavitation erosion. The larger outer diameter of the bearing provides for an increased press fit.
Illustration 1. New 116-3242 Idler Gear Assembly: (1) Bearing (steel-backed aluminum). (A) 105.97 0.01 mm (4.1720 0.0004 in) finished diameter after assembly.The location of the new idler gear assembly in the two front gear groups, as reference in Chart 1, is shown in Illustration 2. Its location in the three accessory drive groups, as reference in Chart 1, is shown in Illustration 3.
Illustration 2. Typical Front Gear Group: (2) 116-3242 Idler Gear Assembly.
Illustration 3. Typical Accessory Drive Group: (2) 116-3242 Idler Gear Assembly.Chart 2 shows the effective engine serial numbers for each of the above 3500 Engines.