DRUM GP 4598605 - Caterpillar

Table 1
Required Tools    
Part Number    Part Description    
9U-4700     Multitach    The pressure settings for the main relief valve and for the crossover relief valves are higher than the setting for the pump cutoff pressure. Therefore, normal system pressures will not open these relief valves. A test for low pressure settings consists of a check of engine rpm under test conditions.
Personal injury or death can result from sudden machine movement.Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.To help prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic and steering system:
Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic systems. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component.Lower all attachments to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the attachment in the raised position, the attachments and lift cylinders must be supported properly.Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.
Move the machine to a clear area that is level. Lower the implements to the ground. Engage the parking brake. Stop the engine.
Install the 9U-7400 Multitach on the tach drive location.
Start the engine and operate the engine at high idle.
Record the high idle reading on the tachometer gauge.
Release the parking brake and engage the service brakes. Move the tiller handle to the MID STEER LEFT position and to the MID STEER RIGHT position.
Record the high idle reading on the tachometer gauge at each position in Step 5.If both of the readings from Step 5 are more than 50 rpm different from the maximum reading in Step 4, then the main relief valve or the crossover relief valves may have low pressure settings.If one reading from Step 5 is more than 50 rpm different from the high idle reading in Step 4, then one of the crossover relief valves has a low pressure setting. The makeup valve in the steering control valve may also be leaking.
Illustration 1 g00611927
Manifold and valve stack (bottom view) (1) Manifold (2) Valve stack (3) Main relief valve (4) Adjustment screw
Steps 7 and 8 determine whether main relief valve (3) or both crossover relief valves have low pressure settings. Turn adjustment screw (4) for main relief valve (3) by 45 degrees clockwise. Repeat Steps 5 and 6.
Illustration 2 g00502559
Counterbalance valve (15) Crossover relief valve for left turn (16) Crossover relief valve for right turn
If both readings from Step 5 are less than 50 rpm different from the high idle reading in Step 4, main relief valve (3) must