ALTERNATOR GP 8Q1942 - Caterpillar

966D, 980C, 988B And 992C LoadersReference: Service Magazine, November 5, 1979, Pages 5 and 6. In the article, "New Hydraulic Control Valve Group Used In Lines And Valve Group," you were told of a new valve group for the 980C Loaders, that permits modulation when the bucket is lowered with the engine stopped. Also, Special Instructions, SMHS7544, tells how to install the new control valve on earlier 980C Loaders. Description of Change: The new lines and valve groups used on all the above loaders have a design which permits this improved modulation with the engine stopped. With these new groups on the 980C, 988B and 992C Loaders the oil from the head end of the lift cylinders flows through the float selector valve to the pressure reducing valve where 2750 kPa (400 psi) oil is made available to the pilot control valve. This oil pressure permits complete control when the bucket is lowered with the engine stopped.On 950B and 966D Loaders the oil from the lift cylinders flows through the combination selector and pressure control valve. This oil then is available to the pilot control valve.
Formerly, oil from the head end of the lift cylinders flowed through the make-up valve back to the hydraulic tank. With this system it was not possible to have acceptable control of the rate at which the bucket was lowered.
Adaptable To: The new lines and valve groups with this improved design are in effect on 950B and 966D Loaders with first built. They are in effect with 980C Loaders (63X1489), 988B Loaders (50W5036) and 992C Loaders (42X869). The new lines and valve groups are in the current Parts Books and microfiche for all these loaders except for the 992C Loaders. The new lines and valve group will be on the next revision of the Parts Book Microfiche for 992C Loaders.