- Articulated Truck:
- 735 (S/N: B1N880-UP)
- 740 (S/N: AXM1-UP; B1P1-UP)
- 740 EJECTOR (S/N: AZZ1-UP; B1R1-UP)
- 740 (S/N: AXM1-UP; B1P1-UP)
Introduction
Operators have been concerned by noise from the power trains of the listed machines. Unnecessary maintenance work has been conducted. This Technical Information Bulletin identifies one source of noise from the power train that can be considered as normal part of machine operation.
References
ReferenceSystems Operation, RENR5134, "740 and 740 EJECTOR Articulated Trucks Power Train", "Rotary Actuator (Transmission)"
ReferenceSystems Operation, RENR5134, "740 and 740 EJECTOR Articulated Trucks Power Train", "Selector and Pressure Control Valve (Transmission)"
ReferenceTesting and Adjusting, RENR5134, "740 and 740 EJECTOR Articulated Trucks Power Train".
ReferenceTesting and Adjusting, RENR5124, "735 Articulated Truck Power Train".
Problem
During operation of the listed machines, excessive noise has been heard from the power train. The noise has caused unnecessary maintenance work on the components of the power train.
The excessive noise can be caused by the normal operation of the power train. The power train can make a noise when a directional shift is made. A noise in the power train can occur when the rotary spool passes through the pressure ports for the reverse clutch and the rotary spool momentarily supplies initial clutch pressure to the reverse clutches. This action can cause the power train to take up the backlash within the driveline with the result of noise from the power train. The noise is normally associated with the driveline from the output transfer gear. The noise is not detrimental to the operation of the machine.
Solution
If a machine experiences functional problems during operational service, check the source of the problem by using standard diagnostic practices. Inspect the transmission filter and the screens for any abnormal debris. Inspect the power train oil filter for any abnormal debris. Check the transmission clutch pressures and torque converter pressures.
If all of the pressures in the power train system are within normal specifications and no abnormal debris is found in any of the filters, the noise from the power train can be considered as normal part of machine operation.
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| Illustration 1 | g01361062 |
Pressure chart of a normal directional shift | |
Normal directional shifts do not cause harm to the driveline components. During a normal directional shift, the initial clutch pressures are low and the engine speed is at low idle. Illustration 1 shows the pressure chart of a normal directional shift.
In this chart, the transmission is being shifted from first gear forward to neutral, first gear reverse and second gear reverse. The chart shows that the pressure for first gear forward suddenly drops off when the rotary spool of the transmission is rotating to reverse. The chart also shows slight pressure rises for first gear reverse and second gear reverse when the pressure for first gear forward drops off suddenly. These slight pressure rises cause the driveline components to change from the forward direction of rotation to the reverse direction of rotation. After the components change direction, the components come to rest against stationary components. This creates the noise in the driveline that can cause the concern.
If the machine is operated according to the Operation and Maintenance Manual for the machine, the noise from the driveline is not indicative of any damage to the power train.
Note: A transmission abuse event (E047 Operator Abuse) is logged if a directional shift is made with the engine speed at 1500 RPM or above. This type of shift over time may reduce the life of some transmission clutches.