QLM’s Guide to Overfilling the Transfer Case – Evo 8/9

How-To: Overfill the Evo 8/9 Transfer Case

This is a walk-through on filling the transfer case on the Evo 8/9. If you are uncomfortable with doing your own work, please consult a professional.


  • 24mm socket
  • 17mm socket
  • Extension
  • Heavy-duty Jack & stands
  • 1 quart of GL5 75w90 (I use Red Line GL5 Gear Oil 75w90)
  • Fluid pump
  • Oil pan

As you are likely aware, the Evo 8/9 t-case needs to be overfilled to be extra safe in making sure the t-case has enough fluid in it. What many shops will tell Evo owners to do is fill the t-case, drive the car around the block, and refill it until fluid comes out. Shops say to do this because it takes time for the fluid to work its way into all the nooks and crannies. I found this method tedious and ineffective. By following the below steps, I can get about 0.9 quarts in the t-case. Do this at your own risk.

1. Drive the car around to warm up the fluid.

2. Jack up the passenger’s side of the car. Always use a jack. Remove the passenger’s side front wheel.

3. Locate the fill plug, which takes a 17mm socket. It can be tricky to access, but I always make sure I can get the fill plug off first. Mine is extra tricky to access/loosen thanks to my RaceFab Oil sump

4. The drain plug is located on the bottom and takes a 24mm socket. Open and drain the fluid. Use an oil pan to drain the fluid, and keep it there.

5. VERY CAREFULLY, lower the car slightly to make sure all the fluid comes out. Loosen the jack very slightly until the car is very slowly creeping down, and lock up once it’s near level. If your jack releases quickly, don’t bother trying this.

6. Once the fluid is done draining, Jack up the passenger’s side as high as you can reasonably get it. Because the fill plug is on the passenger’s side, this will allow you to get in the maximum amount of gear oil.

7. Reinstall the drain plug. I get this reasonably tight, I believe the torque spec is around 30lbft but I always tighten more than that.

8. Use a pump (I used a Plews) and pump fluid in. Connect pump to the transfer case fill hole. Once you get roughly 0.8qts in, you may see some fluid dribble out. Give the fluid a minute to work its way down, and continue pumping until you get nearly a full quart in. Extra oil that leaks out will dribble on the downpipe and cross brace. Position the oil pan to catch the extra fluid.

9. You should have gotten nearly 1 full quart in the t-case doing this method. If not, the car is not jacked high enough. Raise the car & add more fluid. Once the fluid is continuously dripping with each pump, get a few more pumps in and quickly add the fill plug back on, and tighten. This doesn’t need to be super tight, I think the torque spec is also around 30lbft for the fill plug. The job is complete, and no need to drive the car around a block before adding more fluid!


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