0304889 JOHNSON SCREW

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PSP FOR FRONT GEAR TRAIN WEAR ON CERTAIN 3508 ENGINES (50 HZ PRIME POWER GENERATOR SET) - PS4279 - MAILED US AND CANADA, CAC O, COFA, CFEL, COSA
  The information supplied in this service letter may not be valid after the termination date of this program.   Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
U-27 A-18 AU-19 E-15 O-19 1205, 1206, 1313 PS4279 This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS4279" as Part Number, "7755" as Group Number, and "96" as Description Code. Termination Date
February 28, 1990
Problem
Front gear train wear may be a problem on certain 3508 Engines (50 Hz Prime Power Generator Sets only). Installing a larger torsional vibration damper will reduce the torsional vibration and wear.
Affected Product
Model Identification Number 3508 23Z1 - 2128 This Program does not include 3508 Engines sold into standby generator set applications.
Parts Needed
Before Failure 6 - 8S4757 Bolt 1 - 7C9639 Damper Group 1 - 1N3482 Adapter 1 - 5H6734 Seal - O Ring 1 - 6V6809 Seal - O Ring 1 - 6V5066 Seal - O Ring 1 - 1S5772 Gasket After Failure Rework A - Replace Idler Gear & Oil Pump Gear All Parts Listed For "Before Failure" Plus The Following 1 - 7N5241 Gear Assembly - Idler 1 - 7N5250 Gear Assembly - Oil Pump Drive 1 - 7N5243 Bearing - Idler 2 - 8M5255 Seal - Idler Shaft & Water Pump Drive 2 - 7N5244 Bearing - Oil Pump / Water Pump Drive 1 - 1T0132 Seal - Oil Pump Drive Adapter 1 - 6V7681 Seal - Oil Pump 1 - 6V3908 Seal - Oil Pump 1 - 6V5101 Seal - Oil Pump Rework B - Replace Idler Gear, Oil Pump Gear, And Crankshaft Gear All Parts Listed For "Before Failure" and "Rework A" Plus The Following 1 - 7N3049 Gasket - Front Cover 1 - 8N6645 Gear - Crankshaft 1 - 1W6974 Seal Group - Crankshaft 1 - 9M3786 Seal - Required only if equipped with an expansion tank. 2 - 6V1454 Seal - Required only if equipped with an expansion tank. Rework C - Replace Idler Gear, Oil Pump Gear, Crankshaft Gear, And Front Housing All Parts Listed For "Before Failure" and "Rework A" Plus The Following 1 - 7N3049 Gasket - Front Cover 1 - 8N6645 Gear - Crankshaft 1 - 1W6974 Seal Group - Crankshaft 1 - 7W3376* Housing - Front Gear 1 - 7W1529* Housing - Front Gear 1 - 7N5248** Gear - Governor Drive 1 - 7N5875** Gear - Governor Drive 1 - 7N5244 Bearing - Governor Drive 1 - 8M5255 Seal - Governor Drive 1 - 1T0132 Seal - Governor Drive 1 - 7J8114** Gasket 1 - 6V8172** Seal - Lip - Alternator Drive 1 - 7N5241*** Gear Idler - LH 1 - 7N5250*** Gear - Accessory (LH Lower) 1 - 7N5248*** Gear - Accessory (LH Upper) 1 - 7N5875*** Gear - Accessory (LH Upper) 4 - 7N5244*** Bearing - Accessory Drive LH 1 - 7N5243*** Bearing - Idler LH 2 - 8M5255*** Seal - Accessory Drive - LH 4 - 5F3106*** Seal - Accessory Drive - LH 2 - 1T0132*** Seal - Accessory Drive - LH 1 - 9M3786 Seal - Required only if equipped with an expansion tank. 2 - 6V1454 Seal - Required only if equipped with an expansion tank. * As needed. The 7W3376 Housing - Front Gear has left side accessory drive mounting positions. The 7W1529 Housing - Front Gear has no left side accessory drive mounting positions. ** If needed due to gear teeth damage. *** As needed if equipped with LH accessory drives.
Action Required
Before Failure Remove the water pump and inspect the front gear train for heavy wear and cracked or broken teeth. If no damage is found on any of the gears, install the new parts listed for before failure repairs. If damage is found, see the after failure repairs. After Failure If excessive wear or tooth damage has been found, remove the idler