EVO Rear Diff Filling Procedures

It is extremely important that the differential in your vehicle is kept full and clean.  We recommend changing the fluid every 5-10k depending on the type of use and horsepower.  Remember, this unit takes 2 different types of fluids from 2 areas!  Don’t forget to fill one of them or the entire differential will be ruined!

The recommended gear oil, for the diff ring and pinion, in the stock to mid horsepower level street cars is OEM DIAQUEEN Mitsubishi fluid from the dealer.  For high horsepower and/or drag use, we recommend running Redline fluids which ARE NOT shockproof.  Shockproof fluids do not have the friction modifiers needed to allow the Limited Slip to work correctly.

Due to the design and small sump, it is very important to follow the steps below to assure proper lubrication, quiet operation, and a long life.

  1. This method can be used while the fluid is being changed.  This is the messiest way, but is does ensure that the unit is full. (It may require a helper!)
    1. After draining, use a hand transfer pump and insert the hose from the end of the pump into the differential gear oil drain hole.
    2. Tightly wrap a rag around the hose to make a seal.
    3. Continue holding the hose while pumping.
    4. Quickly remove the hose and reinstall the drain plug.
    5. Now you can remove the FILL plug, letting the excess fluid run out through the fill hole.  Filling from the bottom ensures the unit is full.
  2. This method can be used for a fluid change.  Note: This method requires patience as it takes time for the fluid to settle.
    1. After draining, reinstall the drain plug.
    2. Use either a qt bottle or hand transfer pump with a hose on the end and fill the unit through the fill hole.
    3. Due to the design, it is very hard to know when it is full.
    4. The fill hole can push fluid back making you think it is full when it is not.
    5. If using this method it is VERY important to let the fluid settle and try several times to refill to make absolutely sure it is full to the fill plug.
    6. Drive the vehicle around the block.
    7. Pull the fill plug again to assure it is full, if not, add more fluid and go back to step f.

Please note that we spend a lot of time making sure bearing preloads, gear contact, and all seals are perfect and tested before it leaves our facility.  We have also built a machine which can pressurize and test the LSD system for leaks and proper operation in-house.  Every part has been meticulously cleaned with high-end state-of-the-art equipment and checked.  With all of this attention to detail, the unit can be ruined easily as the long ring and pinion contact patch is very unforgiving.  Please be sure to call us if you do not understand the fluid procedures, or where to find the fluid required, so that your new differential will live a very long, and trouble free, service life.

Contact Us

Whether you need a part to complete your build or want us to do it from the ground up, we've got you covered.
Let us take your project 'from Start to FINISH!'

Find Our Shop

Follow Us


3920 North Weber Street Colorado Springs, CO, 80907

Hours: Mon-Fri 8:30AM-7PM MT