Special Report : Reduced Contamination in Diffs and Final Drives

Location: Hunter Valley, New South Wales, Australia

Concerned with highly elevated wear metal debris in the Diff and Final Drive oils of their fleet of CAT 793D haul trucks and the resulting much reduced oil drain intervals, Huddys Mining Services decided to investigate options to manage the wear debris levels in the oil and return servicing costs to acceptable levels.

The haul truck fleet operates in demanding conditions in the Hunter Valley, New South Wales, hauling many tonnes of overburden in preparation for coal mining.

Filter Technology Australia and their Hunter Valley  agent, HVL Group based in Singleton, were contacted to put forward a proposal to clean the oil in service and return the cleanliness to within OEM requirements.

A three month trial was implemented on Unit 707 utilizing an onboard system for 24/7 filtration with clear targets in wear debris reduction and ISO cleanliness levels. Within a month all target levels were well below the required limits with in-service oil running at better than new oil cleanliness levels. Results are since trending consistently.

Huddys have now commenced a program to install Filter Technology onboard diff filtration systems to the remainder of the fleet with strong interest already shown by other fleet owners of mechanical drive trucks.

The FM40325 By-Pass Filtration System is designed to be permanently installed in position on the truck for the filtration of the differential and final drive lube system.

The system is based on the FTA-designed and patented FM2100 Industrial Oil and Fuel Element. This element removes particulate contamination down to 2 micron in size.

FM40325 By-Pass Filtration System

In order to provide effective filtration, the system is sized to provide a filtration flow rate of a minimum 20% of the compartment volume per hour. It is critical to ensure the required turn-over of oil through the filters to remove and maintain contamination levels within the target range.

In the CAT 793D application, oil supply to the FTA filters is taken from the OEM supply to the existing Diff Lube Filtration System. Oil is returned from the FTA filters direct into the diff compartment via an inspection cover plate at the rear of the diff housing.

FM40325 General Description :-

  • Designed as an onboard, continuous bypass filtration system.
  • Takes oil from existing diff lube circuit and filters direct back to compartment.
  • At 4.5L/min, the system is filtered at the rate of approximately 32% per hour.

The graphs below show the significant reductions in both iron and copper contamination in samples taken from the diff unit. Importantly, after commissioning the FM40325 unit, contamination levels were maintained at consistently low levels, without the need for oil changes.


  • Particle count was maintained at 15/12 to 16/13 while the truck was in service. These results exceed the cleanliness requirements for most new oil!
  • Iron paste found at magnetic plugs was significantly reduced.


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