Caterpillar® Product Information

Salesgram

For Dealer Sales Personnel

November 1995

Cat® 785B/789B RearAxle Improvements

In July 1995, production of several improvements to the 793B rearaxle design was implemented. These improvements will becomestandard on the 785B and the 789B, with no change in the price ofthe base truck, as follows:

785 789Effective Date: December 1995 November 1995Effective Serial Number: 6HK00523 7EK00371

The improvements include:

• Addition of a shroud in the differential which reduces the oil temperature in the axle

• Addition of a filter for the rear axle oil

• Direct lubrication of differential and wheel bearings

• A rear axle monitoring system

A new fiberglass shroud covers almost the entire lower half ofthe differential ring gear. This shroud reduces oil temperaturesby reducing the amount of oil churning inside the differential.Laboratory tests show a reduction in temperature of as much as20%. The amount of temperature reduction depends on thelength of the haul cycle; longer, high speed haul cycles will seea greater temperature reduction than shorter cycles. Reducingthe temperature of the oil will better maintain the proper oilviscosity for gears and bearings, favorably impacting axlecomponent life. This shroud will also equalize the oil levels oneach side of the axle.

A gear pump and filter have been added to this major powertrainsystem to provide positive oil filtration and lubrication. A 40micron oil filter has been added to remove debris in the system.Obviously, any debris in the system will adversely affectcomponent lives. This filter is located on the rear of the banjohousing and is easily accessible for servicing.

In addition to pumping oil through the filter, the differentialdriven pump also provides direct lubrication of differential andwheel bearings, ensuring that the proper amount of cool, filteredoil is applied directly to these critical areas. Direct lubricationwill also improve the life of these components.

2

Differential Ring Gear Shroud

Oil Filtration/Direct Lubrication

1

1 - Filter

Cold Oil FlowT<110°F

Thermostat/PressureRelief

Final Drive FlowControl Valve

Differential & Bevel Gear Group

Wheel Group

A system monitoring the rear axle oil, pump, and filter will alertthe operator to potential problems. The system monitors:

• rear axle oil temperature

• rear axle differential pump pressure

• filter (plugged)

On machines equipped with the Electronic Monitoring System(EMS), the system display panel will be located approximatelywhere the TPMS Payload Operator Display is located. TheTPMS Display will be relocated slightly below the displaypanel.

On machines equipped with the Vital Information ManagementSystem (VIMS), the warning system is completely integrated,using the VIMS display pad to communicate system events andthe event recorder when necessary.

3

Monitoring System

TELQ4457November 1995

© 1995 CaterpillarPrinted in U.S.A.