ADAPTER 1167997 - Caterpillar

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 "PS0856" as the Part Number and "7755" as the Group Number. Use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.
Termination Date
June 30, 1996Problem
The turbine wheel of the 7E6836 Wheel and Shaft Assembly in 4P4646 Low Pressure Turbocharger Assemblies may fail in certain 793 and 793B Trucks.
Affected Product
Model & Identification Number
793 (3SJ6-56)
793B (1HL12-176)
Parts Needed
1 - 1193357 Control Group (as needed)1 - 1194755 Plate (as needed)2 - 1220351 Turbocharger Group-Basic1 - 1220562 Plate (as needed)Action Required
See attached rework procedure.
Service Claim Allowances
This is a 24-hour job.
The serial number of the failed turbocharger, found on the turbocharger information plate on the center housing, must be recorded in the warranty claim comments.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
Attach.(1-Rework Procedure)Rework Procedure
1. Remove both 4P4646 Low Pressure Turbochargers.2. Check the engine for:A. Failed high-pressure turbochargers.B. Debris in the engine air intake or exhaust system.C. Failed spacer plates or pushed out injectors in case of a hydraulic lock, all due to a failed 4P4646 Low-Pressure Turbocharger.3. Make sure the engine's two smaller, high-pressure turbochargers are one of the following part numbers: 1064557, 0R6757, 1213850 or 0R6966. These are 56 trim turbochargers. If the engine has 48 trim high-pressure turbochargers (4P4693 or 1098925), the high-pressure turbochargers must be updated in pairs to 56 trim when the new low-pressure turbochargers are installed.4. Install two new 1220351 Low-Pressure Turbochargers.5. Refer to the May 8, 1995 Service Magazine for proper selection of the wastegate orifice plates and control groups (personality modules). Also refer to the August 22, 1994 Service Magazine for modification of the 4P4866 Coupling and 4P4864 Housing for the proper use of wastegate orifice plates if needed. This Program covers only low-pressure turbocharger turbine wheel failures caused by fatigue. Failures resulting from other causes, such as debris in either the oil or air system, are not covered by this Program.
The serial number of the failed turbocharger, found on the turbocharger information plate on the center housing, must be recorded in the warranty claim comments.
6. This step varies depending on the type of engine being reworked:If the engine has Mechanical Unit Injectors, install a 42 mm 1220562 Wastegate Orifice Plate.
If the engine has Electronic Unit Injectors and a regular wastegate, install a 30 mm 1194755 Wastegate Orifice Plate and a new 1193357 Control Group (personality module).
If the engine has Electronic Unit Injectors and a "smart" wastegate, check to verify the wastegate orifice plate has been removed, and that it has a 1248687 Control Group (personality module).No further action is needed.
If the engine has either Mechanical Unit Injectors or Electronic