1987/09/01 Caterpillar

3306B And 3406B (7FB, 8TC) Truck Engines

Description of Change: New turbochargers with new cartridge groups are used on the above truck engines. The new turbochargers, designated by the prefix "C4D" instead of "C4A" in the turbocharger serial number, have the following improvements. See illustration.

... A new 4N7597 Thrust Bearing Assembly (plate) is retained in the center housing by a new 5S4556 Insert instead of being fastened to the center housing with two screws. A dowel pin in the new center housing locates the new thrust bearing.

... The new 5S4556 Insert that retains the thrust bearing in the center housing is a cast plate instead of a stamping. This provides more positive retention of the thrust bearing, and the new insert is easier to remove.

... New alloy in the shaft bearings (part number did not change) reduces wear on the ends.

... The improved 4M8013 Ring-Compressor Seal in the groove around the compressor sleeve is made of different material so it is less likely to be damaged when the seal is installed in the groove. The ring part number did not change.

Locations of the improved turbocharger parts.

... The end clearance of the compressor wheel (part number did not change) is increased 0.13 mm (.005 ").

... Shims are not used behind the compressor wheel for clearance.

... The final tightening torque of the compressor wheel nut for all applications of the new turbochargers on 3306B Truck Engines has been reduced to prevent overtightening of the wheel.

Adaptable To: A new cast insert, new shaft bearings, new compressor and turbine seals, and new shims can be installed on earlier C4A Turbochargers by using a 9Y1669 Kit. Use Special Instruction SEHS8817.

The 9Y1669 Kit is serviced as a kit and contains the following individual parts:

1 - 9Y1134 Insert

2 - 4W7344 Shaft Bearing

1 - 4M8013 Compressor Seal Ring

1 - 4W7354 Turbine Seal Ring

2 - 9B1722 Screw (Thrust Bearing)

4 - 9M8915 Ring (Shaft Bearing Retainer)

1 - 4W7362 Shim (0.08 mm, .003")

1 - 4W7357 Shim (0.13 mm, .005")

NOTE: The kit has a parts service 9Y1134 Insert designed only for use in the former C4A Turbochargers. The new C4D Turbochargers use the previously mentioned 5S4556 Insert. If ONLY the former 4W7348 Insert needs to be replaced, the new 9Y1134 Insert can be used as a direct replacement.

Use the shims in the new kit to reduce the shim pack thickness according to the Special Instruction. See Step 11 on Page 2 for the formula for shim pack thickness.

Use a new final tightening torque on the compressor wheel nut on the turbochargers used on 3306B Truck Engines. These turbocharger compressor wheels have a diameter of 86 mm (3.4 "). Use thread compound and install and tighten the nut to the same initial torque as specified in the Service Manuals for these engines. The additional tightening, after the initial torque, is now60 ° (1/6 turn) instead of 90°.

The final tightening torque for the compressor nut on C4A and C4D Turbochargers on 3406B Truck Engines is still an additional 90 ° (1/4) turn after the initial tightening. These turbocharger compressor wheels can be identified by a diameter of 99 mm (3.9 ").

The former cartridge groups and turbocharger assemblies are canceled.