Mobil1 75W-90 Gear Oil comes default with the Limited Slip Additive already mixed in. The GM Eaton M-Locker Diff Design is NOT a "Limited Slip" style mechanism and calls for this information to be considered for LOCKING Centrifugal Differentials:
LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some Light Duty Trucks equipped with Locking Rear Axles (G80) may Exhibit Rear Axle Chatter, especially when turning a corner from a stop.
This Condition of Alternate Engagement and Disengagement of Clutches in Differential Assembly is usually caused by Contaminated Axle Lubricant.
The Use Of Any Additive In Locking Rear Axles (G80) Is Not Recommended. Rear Axle Additives are Designed for use in Limited Slip Differentials which are Normally Installed in Cars. "All Light Duty Trucks Equipped with RPO G80 Make Use of a Locking Differential" and the Use of Additives will Delay the Engagement of the Locking Mechanism and May Decrease Axle Life.
Rear Axle SAE 75W-90 Synthetic Axle Lubricant (GM Part No. U.S. 89021677, in Canada 89021678) meeting GM Specification 9986115.
WARRANTY INFORMATION:
"As Specified in Light Duty Truck Maintenance Schedules, Locking Rear Axle Fluid Drain and Refill is Required Owner Maintenance at the First Engine Oil Change"......Failure to Drain and Refill the Rear Axle as Specified May Contribute to a Later Axle Chatter Condition. Refer to the Appropriate Light Duty Truck Maintenance Schedule or Service Manual, Section OB, for Further Details on Change Intervals."
Front differential: Fluid type: synthetic 75w90 (GM P/N 12378261, meeting GM Specification 9986115) Capacity: 1.7 pints Transfer case: Fluid type: AutoTrak II (GM P/N 12378508, also listed as GM P/N 88900402) Capacity: 2 quarts Rear Differential: Fluid type: synthetic 75w90 (GM P/N...
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