Usage:
768C, 772B, 776, 776B Tractors;
769C, 773B, 777, 777B, 785 Trucks
- SUPPLEMENT: 03/09/87
SERVICE MAGAZINE; AUGUST 18, 1986; PAGE 6; "New Duo-Cone Seal Groups Prevent Oil Transfer." Disregard the first sentence of the second paragraph in the section, "Description Of Change." The correct information is given in the first sentence of the section, "Adaptable To."
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Description of Change: New Duo-Cone seal groups, with silicone rubber toric rings, are used in the service and parking brake groups on the above machines. The new seal groups are also used in the front wheel bearing compartments of 785 Trucks. The new seal groups will better prevent oil transfer between the brake cooling oil circuit and the final drive/differential/wheel bearing compartments.
The silicone rubber improves low and high temperature characteristics of the toric rings.
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Use only the recommended weight CC, CD or CD TO-2 engine oil with silicone rubber toric rings. SAE 90 weight Extreme Pressure (gear) oil will cause silicone rubber toric rings to disintegrate. Mark final drive covers, differential case and front wheel bearing covers to indicate the use of CC, CD or CD TO-2 oil to prevent any accidental use of EP (gear) oil.
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Adaptable To: The new Duo-Cone Seal Groups have a 15° ramp angle and are direct replacements for former seal groups with 15° and 8° ramp angles as shown in the chart.
The new silicone rubber toric rings are yellow in color and are a direct replacement for the former Buna-N (black) and Viton (blue) rubber toric rings used with former seal groups. The new toric rings cannot be used with earlier seal groups that have an 8° ramp angle. To use the new silicone rubber toric rings, seal groups with an 8° ramp angle must be replaced by a complete seal group that has a 15° ramp angle.
If repairs are made to the final drive group of a truck, replace any outer Duo-Cone Seal Group that has accumulated over 1000 hours of operation. Normal wear of the outer seal group will prevent "perfect" seal face alignment if the seals are reused. If the seals do not align correctly, leaks will develop.
When inspecting or making repairs to final drive groups or wheel bearings, carefully inspect the wheel bearings for signs of spalling which may indicate a lack of lubrication caused by the transfer of hydraulic oil from the brake cooling circuit. Replace any damaged wheel bearings and adjust bearing preload, as described in the Service Manual, so that the Duo-Cone Seal faces are in the correct position.
785 Trucks have oil cooled front brakes. If a massive failure of the front wheel bearings occurs, remember to clean the hydraulic tank and change all hydraulic system filters and screens.