How To

How to Fill a Rear Differential

By Valerie David, eHow Editor
Rate: (2 Ratings)

You may need to add fluid to your differential due to leaks or changing seals, or it may be time to change out the gear oil completely. Either way, it's just a few steps to fill the rear differential and get your vehicle back out on the road!This article will explain how to fill a rear differential.

Difficulty: Moderate
Instructions

Things You'll Need:

  • 3/8 inch drive ratchet with extension
  • 2 quarts gear oil (gear lube, differential fluid)
  • Side cutters
  • Oil drain pan
  • Shop rags
  • Flashlight or shop light (optional)
  • Lock tight (optional)

    Filling a Rear Differential

  1. Step 1

    Be sure the car is raised on four jack stands and is level. It will be more difficult to fill the differential if you've only got it raised in the rear.

  2. Step 2

    Place an oil drain pan underneath the plug to catch any leaks or drips. Keep shop rags handy for any spills.

  3. Step 3

    Check your service manual for the amount of fluid your differential needs, if you're completely refilling the system. Two quarts should be enough in most cases.

  4. Step 4

    Remove the spouts on the gear oil containers. Peel off seals, then replace spouts. Use side cutters (or any cutting tool you've got handy) to clip off the top of each spout.

  5. Step 5

    Remove the differential fill plug using a 3/8 inch drive ratchet with extension. (Some models may require a hex key or screwdriver, but the 3/8 inch is the most common plug design.)

  6. Step 6

    Take the gear oil container and fit the spout into the fill hole. Pour the fluid inside. You can gently squeeze the bottle to speed the process. Repeat with a second bottle if necessary.

  7. Step 7

    Fill the differential until the fluid starts draining back out of the hole.

  8. Step 8

    Clean and replace fill plug. Use lock tight (thread locker) to help seal if desired. You can see my eHow article "How to Replace Rear Differential Fill Plug" for more information.

  9. Step 9

    Take the car for a drive around the block to get the gear oil moving. When you return, check underneath for any leaks from the fill plug or differential cover.

Tips & Warnings
  • It's a good idea before you add gear oil to check that the differential cover is sealed and tightened with the proper torque. For a complete change of fluid you'll have to drain and reseal the system before refilling it. You can get more information in my eHow articles "How to Drain a Rear Differential" and "How to Torque Rear Differential Cover".
  • Always follow the manufacturer's instructions and warnings when dealing with fluids, cleaners, and sealants.
  • Differential fluid has a noxious odor. Be sure to work in a well-ventilated area!

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