Usage:
789B (7EK),
793B (1HL) Trucks
Description of Change: A new flywheel assembly is used. The new flywheel assembly has four oil drain passages instead of the two drain passages on the former flywheel assembly. Initially, the four drain passages were 8.0 mm (.31 in) in diameter. They have since been enlarged to 11.0 mm (.43 in) in diameter. The former flywheel assembly could limit the ability to quickly drain oil from the flywheel housing at startup because of its two smaller drain passages. This could create an excessive hydraulic force on the crankshaft causing it to move forward and wear into the rear crankshaft thrust bearing. The new flywheel assembly with four larger drain passages will limit this force.
Adaptable To: The new 106-4705 Flywheel Assembly is a direct replacement for the former 4W-7640 Flywheel Assembly. The new flywheel assembly with the four 8.0 mm (.31 in) in diameter oil drain passages went into production effective with 789 and 793 replacement engine serial number 54Z946, 789B (7EK159), and 793B (1HL41) Trucks. The new flywheel assembly with the four 11.0 mm (.43 in) in diameter oil drain passages went into production effective with 789 and 793 replacement engine serial number 54Z970, 789B (7EK210), and 793B (1HL78) Trucks. The new flywheel is adaptable to first production. The former flywheel can be salvaged by enlarging the two existing 8.0 mm holes to 11.0 mm and adding two more holes. Also, the four oil drain passages on the new 106-4705 Flywheel Assembly are equally spaced every 90°. The two oil drain passages on the former 4W-7640 Flywheel Assembly are 180° apart. The illustrations shows the locations and dimensions of the oil drain holes in the new flywheel assembly.
Illustration 1. Locations of the four equally spaced oil drain holes. (B) 556.0 mm (21.89 in) Diameter - This is the diameter at which four holes (E) are drilled to intercept four holes (D). (C) 470.0 mm (18.50 in) Diameter - This is the diameter at which four holes (F) are drilled to intercept four holes (D).
Illustration 2. (View A-A). 1H-0974 Dowel (1). Dimensions for the four oil drain holes: (D) 11.0 mm (.43 in) Diameter, 85.0 mm (3.35 in) Deep; 12.50 ± 0.13 mm (.492 ± .005 in) Diameter; 14.0 mm (.55 in) Deep; Four equally spaced holes. (E) 11.0 mm (.43 in) Diameter, 62.0 mm (2.44 in) Deep; Four holes. (F) 12.0 mm (.47 in) Diameter, 12.0 mm (.47 in) Deep; Four holes. (G) 89.41 ± 0.25 mm (3.520 ± .010 in) Dimension for locating four equally spaced holes (D)