DIY: Differential Fluid Change- Basic (RC only)

Discussion in 'How-To/Tech Database' started by Kevan, Jan 30, 2008.

  1. Kevan

    Kevan SRT-10 Owner

    Likes Received:
    Dec 15, 2007
    New Albany, OH

    Here's the tools we'll need:

    • Oil catch pan
    • 3/8" drive socket wrench
    • 4" extension (3/8" drive)
    • 8" extension (3/8" drive)
    • Torque wrench (ft. lbs.)
    • Wire cutters (for opening diff. fluid bottle nozzles)
    • Pump with hoses
    And here are the supplies needed:
    • (3) quarts of differential fluid (your choice)
    • (1) 4 oz. tube of Limited Slip Additive
    • (1) tube of silicone sealant (the black tube)
    • (1) tube of thread sealant (the gray tube)
    • (1) roll of paper towels (or shop rags)
    First, remove the spare. You'll need as much room as possible under there.
    Next, we need to setup the truck for proper drainage. At the very least, it should be on a level surface. If you can, ramp up or jack up the front of the truck. This will help remove ALL of the differential fluid as gravity usually wins.

    Place your drain pan under the differential. Make sure you have enough room to spare because the fluid isn't going to drip- it's going to flow quite heavily, like pouring milk out of a carton:

    Using your 3/8" socket wrench and the extension, carefully remove the drain plug located at the bottom of the diff. cover:

    You'll notice that the fluid begins to slowly flow out:

    Keep unthreading the plug, and enjoy the flow:

    Be careful as you remove each plug because they both have a magnetized tip. This magnet collects the small chips (swarf) and other nasty bits that would cause damage to your differential. Here's the bottom drain plug with all sorts of crap on it:

    And here's the top fill plug, again with more crap on it:
    If you so desire, you can save this swarf and have it analyzed or simply wipe it away. Before re-inserting either plug, make sure the magnetic tips are clean.

    Here we have both plugs out, to allow plenty of air in the top so fluid can come out the bottom:

    Now, go watch the latest release from Krystal Steal and wait for the fluid to fully drain. As this is very thick 'oil', it will take a decent amount of time for it all to come out.

    Enjoy an adult beverage while it finishes up.
    Check the air pressure in your tires.
    Windex the windows (inside and out).
    Now go back and wipe the front face of the diff. and check to see if it's still flowing. If yes, find more stuff to do. If no, then move on to the next step.

    Apply some silicone thread sealant to the threads on the drain plug (top to bottom), and install the drain plug:

    Torque the drain plug down to 20 ft. lbs.:
    Some sealant may bead up along the outer edge. Leave it alone and let it dry. We'll clean it up later.

    Now we're ready to add fluid. First thing to do is lower the front end of the truck. Make sure it's as level as possible. If the nose is up at all, you won't put in enough fluid; if the nose is down, you may add too much fluid and blow out seals or cause other damage.
    When you're level, add the Limited Slip Additive (aka LSA). This comes in a 4 oz. tube, so you want to add all of it.
    Keep your drip pan under the diff. cover just in case any slips out.

    Some folks like to pour right from the bottle into the diff. If that's you, and you're using Mobil 1 fluid, remove the paper seal under the nozzle:
    You don't want to know how I found out about that. :)

    Some folks (like me) prefer to use the pump:
    $10 at most auto stores or Wal-Mart. Worth every penny.
    Make sure your tube goes into the diff. housing and *stays* in there as you're filling up.

    The manual says "3.5 qts." of fluid for the diff. Mine was full at exactly 3 qts. You'll know when it's full when the new fluid starts to drip out of the bottom edge of the fill hole:

    Apply thread sealant (top to bottom) on the fill plug and put it back in the diff. cover:

    Torque the fill plug to 20 ft. lbs.:
    Again, we'll have some of the thread sealant bead up on the outside. That's fine, leave it for now. We'll come back to it once it's dry.

    Use a shop rag or paper towel and clean up any fluid that might have dripped down from the fill hole.

    After wiping down the diff. cover thoroughly, lay down a clean paper towel and place it under the differential. This will tell you if you have any leaks.
    After 4 hours:

    After 8 hours:
    Looks good.

    Now is a good time to get rid of that extra thread sealant. You can use your X-acto blade and trace around the edge, or simply wipe it away.

    It's time to take it for a drive around the block. You should notice that when in gear and off the throttle, the truck is smoother as it rev's down. That's your new fluid doing it's job!

    After the test drive, come back and put another clean paper towel down under the differential and let it sit overnight (use a wrench to hold it in place). Check for any leaks.

    There ya go! Your differential fluid has been changed and ready for another few thousand miles.


    ©2007 Kevan J. Geier
    All Rights Reserved
    Last edited: Oct 22, 2008