RING-BACKUP 6E0771 - Caterpillar

Caterpillar: Confidential Yellow
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.
This Program can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS0530" as Part Number, "7755" as Group Number, and "96" as Description Code.
This Revised Service Letter replaces the August 29, 1991 Service Letter and the October 12, 1991 Service Letter Supplement. Changes have been made to the Affected Product and Parts Needed.
Termination Date
August 31, 1993Problem
The rear cam drive gear groups on certain 3512 and 3516 Industrial, Marine and Generator Set Engines may be found with pitting or broken teeth on the small gear of the cluster gear assembly and the idler gear assembly. The bolts that retain the idler shafts to the cylinder block may be loose or broken and/or the idler gear bearings may be found to have pitting.
Affected Product
Model & Identification Number
Group 1 Affected Product require new gears. Group 2 Affected Product do not require new gears.
Group 1
3512 65Z602-611,65Z622,65Z628-631,65Z634-637,65Z642,65Z645-654,65Z656,65Z658-662,65Z664-673,65Z675,65Z680-685,65Z689-698,65Z708-713; 66Z190-208,66Z211-228,66Z230,66Z232-243,66Z245-254,66Z256-261,66Z264-271,66Z273,66Z275,66Z277-280,66Z282,66Z289,66Z291-311,66Z313,66Z314,66Z316-318,66Z320,66Z322-327,66Z330-338,66Z340,66Z343-346,66Z348,66Z349,66Z352,66Z358,66Z361,66Z364,66Z367,66Z369,66Z374,66Z375,66Z377,66Z378-390,66Z393-404,66Z406-414,66Z416-422; 67Z535-540,67Z542,67Z545,67Z547,67Z551-553,67Z556,67Z559,67Z564-567,67Z573-579,67Z581-584,67Z588-598,67Z600,67Z602,67Z603,67Z605,67Z607-622,67Z624,67Z628-631,67Z633-635,67Z638,67Z643-656,67Z670-680,67Z682,67Z683,67Z688,67Z689,67Z691-712,67Z714-719,67Z721-723,67Z725-729,67Z731,67Z732,67Z734-736,67Z738,67Z740,67Z745-751,67Z754,67Z758-761,67Z763-770,67Z772-779,67Z784,67Z785,67Z787-804)
3516 (25Z684-2266) (50 HZ Generator Sets Only); 71Z1-241,71Z244-252,71Z257,71Z263-273,71Z283,71Z284,71Z288,71Z291; 72Z1-338,72Z355,72Z356,72Z366,72Z376,72Z377,72Z380,72Z384,72Z385,72Z391; 73Z174,73Z175,73Z178,73Z179,73Z181-190,73Z193-203,73Z205-207,73Z209-219,73Z221-232,73Z236-250,73Z252,73Z254-304,73Z306-311,73Z313-324,73Z326,73Z328,73Z331-333,73Z335,73Z344-356,73Z365-372,73Z374,73Z376,73Z378,73Z380-383,73Z388,73Z391,73Z392,73Z395-404)
Group 2
3512 (65Z716-723; 66Z423-433; 67Z794-828)
3516 (71Z297-301)
Parts Needed
Use as required. Refer to the May 13, 1991 Service Magazine article "Rear Gear (Cam Drive) Groups Improved" to determine which parts are required for specific engines.
Group 1
4 - 1B4367 Bolt3 - 4B8407 Gasket2 - 7E3897 Gear-Cam Drive1 - 2J6274 Seal1 - 9L1480 Gasket3 - 4M6853 Gasket2 - 4N0933 Gasket1 - 7N3049 Gasket2 - 7N4320 Gasket2 - 4P5090 Shaft-Idler2 - 4P5091 Washer-Thrust1 - 4P5437 Shaft-Cluster2 - 4P5440 Gear Assembly-Idler1 - 4P5441 Gear Assembly-Cluster4 - 1V6341 Seal-Magnetic Pickup (wet flywheel housing only)1 - 1W6977 Crankshaft Seal Gp. (standard rotation engine only)1 - 1W6974 Crankshaft Seal Gp. (reverse rotation engine only)Group 2
4 - 1B4367 Bolt3 - 4B8407 Gasket1 - 2J6274 Seal1 - 9L1480 Gasket3 - 4M6853 Gasket2 - 4N0933 Gasket1 - 7N3049 Gasket2 - 7N4320 Gasket2 - 4P5090 Shaft-Idler2 - 4P5091 Washer-Thrust1 - 4P5437 Shaft-Cluster1 - 4P5438 Bearing-Idler Gear*1 - 4P5439 Bearing-Idler Gear*4 - 1V6341 Seal-Magnetic Pickup (wet flywheel housing only)1 - 1W6977 Crankshaft Seal Gp. (standard rotation engine only)1 - 1W6974 Crankshaft Seal Gp. (reverse rotation engine only)* See Special Instruction SEHS9282 for information on machining these bearings after installation in the gears. Also, see Service Magazine Supplement June 17, 1991.Action Required
Follow the procedures in the Service Manual for removing the flywheel housing and gears. Refer to the May 13, 1991 Service Magazine article "Rear Gear (Cam Drive) Groups Improved".
When installing the new 4P5090 Idler Gear Shafts, follow instruction in Guideline For Reusable Parts, Form SEBF8166, "Salvage Procedures For Bolt Holes in the Block For Idler Gear Shafts In Rear Gear Train 3500 Family of Engines."
Service Claim Allowances
This is a 30-hour job.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.