Differential Gear Oil: Inspection

Park the vehicle on a level surface.
Remove the collector cover.
NOTE: Follow the steps below when removing the collector cover.
1. Pull up the two points at the rear (A).
2. Pull up the two points at the front (B) while moving them forward.
  
  Fig 1: Removing Collector Cover
  Courtesy of SUBARU OF AMERICA, INC.
Remove the oil level gauge and wipe it clean.
Reinsert the level gauge all the way. Make sure the level gauge is inserted correctly and in the proper orientation.
Remove the oil level gauge again, and check the level of differential gear oil. If the differential gear oil level is below "L" line, add oil to bring the level up to "F" line.
NOTE: To prevent overfilling the differential gear oil, do not add oil above the "F" line.

Fig 2: Checking Automatic Transmission Fluid Level Using ATF Level Gauge
Courtesy of SUBARU OF AMERICA, INC.