RX8 Transmission and Differential Oil Change

Along with the other maintenance related DIYs served on this website. Another important set of fluids that should be changed on vehicles that frequent the track are the transmission and differential oils.

Requirements

I have tried various fluids over the years of my ownership and I always find myself coming back to a particular set of fluids for both my transmission and my differential. For this tutorial, you will want to pick up 2 quarts of Ford Motorcraft Full Synthetic Manual Transmission Fluid for the transmission, and 2 quarts of Red Line Lightweight Shockproof Gear Oil for the differential.

For the S2 transmission, I have found the Ford fluid to be the smoothest and there have been various forums that have promoted its use as well. I have tried Red Line's MT90 fluid in the past and unfortunately didn't have great experience with shift feel. Take note, as referenced in the above picture, you will want to pick up a set of replacement crush washers for an optimum seal.

• 2x 1 Quart Ford Motorcraft XT-M5-QS
• 2x 1 Quart Red Line Lightweight Shockproof Gear Oil
• 4x ISH9956-41-800 Mazda Crush Gasket
• 1x 24mm Socket

Word of Warning

This should go without saying, but please, ensure that you are following the proper safety guidelines when performing any DIY on your vehicle. For this particular DIY, it is recommended that you place your car on a four corner set of jackstands. This will ensure that you are provided with ample room to work, as well as a secure environment for your vehicle. Please never work on your car supported only by a jack.

Start Draining

Using your 24mm socket, the first thing you want to do is crack open the FILL plug on both the transmission and the differential. The reason you do this is to ensure that you can get the filler plugs off and arent stuck with a fully drained transmission and no way to fill. Once you get the filler plug loose, crack open the drain plugs and let them drain their fluids.

Take note, the filler plugs are always the plugs that are sitting near the top of the hardware, while the drain plug is sitting near the bottom.

Clean the Plugs!

One thing you will want to do while the fluids are draining from your transmission and differential is to clean the drain plugs. On both drain plugs, you will find a magnet that is used to collect any metallic particals that are floating around the cases. Fine particles are common especially if this is your first time changing fluids. If you do however find large pieces of shrapnel, you may want to consider further investigation to ensure the integrity of the transmission/differential. The image below is that of the differential drain plug

One last thing to note before you replace the drain plug is to ensure that the old crush washers were removed. On both my differential and my transmission I found that my drain plug crush washers were stuck. A quick tap with a flathead screwdriver got them right off.

Fill and Button Up

Once you have fully drained the system, grab a brand new crush washer, and replace the drain plugs. Both plugs have similar torque specs. See below for reference

Finally, use a fluid transfer pump to start filling the fluid back up. It is recommended to fill both the transmission and the differential with fluid until the fluid reaches the filler plug hole. I personnally fill until I see overflow start to come out of the filler plug. Replace the filler plug with a brand new crush washers and clean the plug area of any fluid to reduce the burnoff smell from driving. Once complete, you may now carefully lower the vehicle.