2010/12/08 Caterpillar

Wheel Tractor-Scraper:

621G (S/N: DBB1-UP; CEN1-UP; ALP1-UP; CEP1-UP; DBX1-UP)

623G (S/N: DBC1-UP; CES1-UP; ARW1-UP; CEW1-UP; DBY1-UP)

627G (S/N: DBD1-UP; AXF1-UP; CEX1-UP; CEZ1-UP; DBZ1-UP)

631G (S/N: DFA1-UP; DEM1-UP; CLR1-UP; CMT1-UP)

637G (S/N: CEH1-UP; CEJ1-UP; DFJ1-UP; CEM1-UP; DEX1-UP; DEY1-UP)

Service Magazine SEPD1215, 08 December 2010, "The Main Control Valve Is Updated on the Engines of Certain Wheel Tractor Scrapers". Disregard this article. Refer to the article that follows.

Description of Change: A new relief valve is now used in the main control valve. The new relief valve has a longer shaft. The longer shaft will not come off-center. When the shaft comes off-center, the relief valve sticks in the open position.

Adaptable To:

Illustration 1	g01402879
(1) Location of the relief valve groups

The new 300-6141 Relief Valve Gp is a direct replacement for the former 9T-7184 Relief Valve in the 156-2659 Main Control Valve Gp. The new 307-1647 Relief Valve Gp is a direct replacement for the former 6E-2732 Relief Valve Gp in the 156-2656 Main Control Valve Gp and the 239-1262 Control Valve Gp .

The new relief valve groups are adaptable back to the beginning of production on the machines. The new relief valve groups became effective in production with the following machines: DFA318-UP, DFJ342-UP, DBB576-UP, DBD757-UP and DBC399-UP