Differential Gear Oil Fluid Check

Step by step instructions on how to check and add gear oil to an automotive differential. This article pertains to all rear wheel vehicles.

Difficulty Scale: 2 of 10

Tools and Supplies needed

  • Flashlight
  • Appropriate 3/8 ratchet, socket or wrench
  • Gear oil
  • Shop towels
  • Protective eyewear and gloves

Start with the vehicle on level ground, safely lifted to access the differential fill port, use jack stands to support the vehicle.

Step 1
- Locate the gear oil fill port on the differential housing or rear cover.

Gear Oil Fill Port

Step 2 - Once located use the appropriate tool to remove the fill port plug.

Remove Gear Oil Fill Plug

Step 3 - After the plug has been removed, insert a finger or wire into the fill port.

Insert Gear Oil Level Checker

Step 4 - While inserted the indicator will leave a gear oil trace when removed. (Note: do not turn drive shaft or rear wheels while checking the gear oil level.)

Level Indicator Inserted


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-07)