Usage:
All Series Of 768, 772, 776 Tractors and 769, 773, 777, 785, 789 Trucks
- SUPPLEMENT: 11/13/89
SERVICE MAGAZINE; SEPTEMBER 5, 1988; PAGE 5; "Lists Of Duo-Cone Seals And Oil Recommendations" on all series of 768, 772, 776 Tractors and 769, 773, 777, 785, 789 Trucks. Add the following information to the first paragraph in the "Description of Change."
NOTE: The change interval for the final drives and differential in 789 Trucks is STILL 2000 hours because these compartments use EP oil.
Engine (CD) oil is used in the final drives, differentials, and front wheel bearings of all current off-highway tractors and trucks, except 789 Trucks (see above note). Engine oil is used because it is compatible with silicone that is now being used in the Duo-Cone toric seals in the rear wheels on all of these machines, and in the front wheels on 785 and 789 Trucks. Gear oil MUST NOT be used with the silicone seals.
Disregard the information on the S·O·S indicators in the original article. The following S·O·S indicators better define the maximum values or wear particle limits. At these values, the oil is contaminated and its useful life has been reached. Change the oil when either or both of these values are reached.
...768, 772 Tractors and 769, 773 Trucks (all series): 300 ppm of iron and/or 25 ppm of silicon.
...776 Tractors and 777, 785 Trucks (all series): 250 ppm of iron and/or 10 ppm of silicon
--------------- END SUPPLEMENT ---------------
Reference: Service Magazine; August 18, 1986; Page 6; "New Duo-Cone Seal Groups Prevent Oil Transfer".
Reference: Previous Service Magazine articles have announced new Duo-Cone seal groups and changes in the recommended oil for the above models. This article includes all the information on the new oil recommendations, as well as a chart listing the current seal groups and toric ring for all locations on all the above models.
Description of Change: For approximately one year, the current models of the above trucks and tractors have been shipped from the factory with API CD SAE 50 grade engine oil in the final drives, differentials, and front wheel bearings, except for the final drives and differential in 789 Trucks which still use EP oil. Also, the oil change interval has been extended from 2000 hours to 4000 hours, or IF monitored with the S·O·S Program, the interval is based on the condition of the oil. The change indicators are either 300 ppm of iron or 25 ppm of silicon.
The main reason for using engine oil is because it is compatible with silicone now being used in the Duo-Cone toric seals in the rear wheels on all the above series trucks and tractors, and in the front wheels on the 785 and 789 Trucks. Gear oil MUST NOT be used with silicone-type seals because it causes these seals to swell and soften resulting in leaks. A secondary reason for using engine oil is that the change interval can be longer.
Recently, new Duo-Cone seal groups (15°) became available for parts service. The toric rings and metal seals are the same, but each new group part number includes an installer tool and an installer gauge. This makes the tools readily available to the serviceman, and helps to assure long seal life. See chart.
Adaptable To: The new and former seal group part numbers, and their location are listed in the following chart.
When it is necessary to replace any 8° or 15° BUNA-N or VITON seal groups, install the applicable new seal group in the chart. Do NOT mix parts in the former and new groups.
Caterpillar recommends that the appropriate type and viscosity of engine oil be used in the three compartments the next time the oil is changed. This applies to all current and noncurrent trucks and tractors listed in the title. See the following chart for type and viscosity of oil to use. The viscosity/temperature ranges are the same as already published for differentials and final drives in many Operation and/or Maintenance Manuals for other Caterpillar products. (As previously stated, the listed trucks and tractors are shipped with API CD SAE 50 engine oil in the affected compartments.)
By changing to engine oil in the field, regardless of the type of toric seals used, the oil will be compatible to either the former or new seal material.
Use an oil meeting one of the following requirements:
... API service category CD, or CD/TO-2, or CC in SAE grade 5W-20 SPC, 10W, 30, 40, or 50,
... or, MIL-L-2104D, or MIL-I-46152B in SAE grade 10W, 30, or 40.
NOTE: Refer to all the Operation and/or Maintenance Manuals for all the listed trucks and tractors. Add a Note to the Lubrication and Maintenance Chart referring to this later Service Magazine article.
As soon as possible, the stocks of Guides for the affected machines will be changed.