Need help changing rear diff fluid.

Discussion in 'Chevy Truck Talk & GM News' started by Outlaw19, Feb 4, 2014.

  1. Outlaw19

    Outlaw19 Member

    I have a 2000 Chevy 1500. I'm not sure what one is the drain and fill plug. there's one that is on the diff cover and one that is near my driveshaft. The one near my drive shaft wont come out so im hoping this isn't my fill plug|???? also what kind of diff fluid should I use in a 2000 chevy Silverado with high milage.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    In the Diagram, Number #37 is the Drain Plug....Number #38 is the Fill Plug, and Number #39 is the Connector for a Vent Hose .....and you want to go with 75/90 Gear Lube....make sure to Clean the Cover before Re-Installing it....I'm running with 75/90 Gear Lube from Royal Purple in my Rear Diff.


    Edit:....I would also add, if you have RPO Code G80 ...........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.

    ***You'll need to Buy 3-Quarts of Gear Lube, as your Rear Diff takes 2.15 Quarts to Fill.
    Last edited: Feb 5, 2014
  3. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

    also do not drain if the fill plug wont come loose. Always loosen the fill plug first.
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    What the guys above have said is all good; however (ya just knew I was going say that, haha), if there is a plug in the rear cover, and it is in the middle, or higher, of the cover, you can use that (if it's below the middle, it might be an additional drain plug). I suspect it is a fill plug.

    That is probably an after market diff cover and it is designed to be removed for lub changes and has the plug for filling.
  5. Outlaw19

    Outlaw19 Member

    rear diff.jpg Heres a picture of what my rear plug looks like. Is this a fill port or drain plug.
  6. Boonduff

    Boonduff Rockstar 4 Years 100 Posts

    That is a fill plug. Look at the very bottom of the housing you will probably find another plug. That will be your drain plug. If there is no plug there, you will have to remove the cover to drain the fluid.
  7. Outlaw19

    Outlaw19 Member

    I found the drain plug underneath. So are you sure that the plug in the centre is my fill plug?

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    x2...on that being the Fill Plug in the Picture you've posted, also some Rear Diff's don't have a Fill Plug on the Cover.....its located on the side of the Diff.....Number #38 in the Diagram.

    Also this Video shows where the Fill Plug is located, if there's not one on the Diff Cover.
  9. Camaro69car

    Camaro69car Member 2 Years 100 Posts

    positive. you should be able to put your finger through that hole, and the fluid should be close to where that bolt sits, thats how you know you're full.

    the lower bolt is for draining the fluid out.

    Things to look at:

    1: Make sure you can get the fill plug out first. (to make sure you can fill it after you drain the fluid)
    2: Drain fluid and inspect for metal shavings.
    3: Unbolt cover and clean old fluid off.
    4: Inspect rear end gears for wear.

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