How To: Diff Oil change

How to Change Differential Oil

Knowing how to change the differential oil is important when servicing your car or making adjustments to the differential setup. Changing the oil is an easy and simple thing to do when you’ve got your car on a desk.

Needed tools:

• Proper tools for the screws
• Pliers
• Paper towels to protect the desk
• Differential oil

Start the process by covering the desk with for example kitchen paper that will absorb the oil.

Next, remove the differential from your car. In newer cars you only need to open the housing cover and remove the differential. Use a paper towel, and if needed, soap, to clean the differential.

Next, remove the cover. At this point, it’s good to get rid of the old oil/grease.

Next, remove the small internal gears to make it easier to clean the differential case properly and to check the condition of the gears. If the differential has leaked, it may be a good idea to replace the O-rings of the outdrives with new ones.

Tip! Use thin-ended pliers to get a good grip on the gears. However be careful not to scratch the axles of the small gears. The easiest way to remove the pins of the outdrives is by using pliers.

After a thorough cleaning, check the condition of the cover seal and seat it back on properly. Add the oil in two stages.

• Start by placing the gear at the bottom of the differential. Next, add oil so that the edges of gear are covered (not all the way up!).
• Next, place the small gears on top of the gear. Place the gears on the cross axle and place the entire thing inside the differential. If the differential has four gears (axles are crossed) make sure that the flat parts of the axles are matched properly. This way, the oil already in the diff will get into all the nooks and you don’t have to wait so long for the air to get out of the diff.
• Finally, add some more oil until the cross pins are covered.

Note! When adding oil, make sure to leave enough space for the gear on the cover to fit in. If the differential is filled up too tight, it will likely start leaking. On the other hand, if there isn’t enough oil, the oil will foam during long runs and the oil won’t lubricate the gears the way it should.

Note! Let the oil sit in the differential for a while before putting the cover back on. The thicker the oil, the longer it takes for it to settle between the gears and for the air to get out.

If your car has a so called planetary gear differential (for example Traxxas 2WD, Losi 22–4), the gears are placed each on their own axle in the diff housing. After this, add the oil and make sure that there’s enough space for the cover gear.

Finally, put the cover back on. At this stage, make sure that the cover seal is seated correctly with the screws. Start by tightening the screws lightly and then adjust tightness carefully by cross-tightening the screws.

After tightening, make sure the differential spins smoothly and is not leaking oil. Finally, install the differential in opposite order to when removing it.