BUSHING 2A3195 - Caterpillar

5. Check the servo valve adjustment. If servo valve adjustment is not correct, travel conditions (terrain) can cause pressures in the track circuits that are high enough to cause the pump to stroke. Typically this problem would not show up if testing is done on a hard level surface. Check the adjustment of the servo valve as follows if it is suspected as the cause of travel drift.a. Disconnect the pump control signal lines from the pump heads.b. Plug the lines and leave the signal ports open to the atmosphere. This will cause the pumps to remain at full output and prevent them from stroking.c. Check the condition of the servo cartridge O-ring seal at this time.d. Allow any oil that has been trapped in the servo signal port to drain. Check the amount of leakage at the pump signal port while operating an implement at relief valve pressure. Check one pump at a time. The maximum permissible leakage is 6 to 10 drops per minute.6. Check for excessive clearance between the main control valve stem and the valve housing. Be sure the valve stem is shifting fully. Check for excessive clearance and leakage in relief valves, make-up valves, swivel seals and track motors.7. Check for a restriction in the motor discharge circuit (motor to tank return line), or the control valve pilot line.8. Check for mechanical (non-hydraulic) causes for travel drift.a. Make sure both tracks are properly adjusted.b. Check for seized track pins and bushings.c. Check for correct final drive bearing adjustment.d. Make sure brakes are not dragging on either side.9. Make sure the centering or load springs are properly adjusted. If travel drift in forward is not in the same direction as travel drift in reverse, centering shims must be added.10. Adjust the load shims if travel drift is in forward or reverse only. If travel drift is in the same direction in forward and reverse, adjust the load shims. When load shims are properly adjusted, pilot pressure to start track movement should be approximately 620 to 760 kPa (90 to 110 psi). Later 245 Excavators and 245 Front Shovels have external load spring adjusting screws at the ends of the valve housings.11. Make sure the load springs have the same spring rate.12. Check travel drift at "dead slow" pedal (inching). If the machine attempts to turn at pressures just high enough to cause movement of the tracks, the following should be checked.a. Make sure the travel spool to valve housing timing is correct. The motor to tank port must open before the pump to motor port opens.b. Make sure the overspeed valve is not sticking.