Whether driving an Infiniti G35 sedan or coupe, changing the differential oil on a regular basis is as necessary as changing the motor oil. The friction caused by daily use, particularly when turning, can cause premature failure of the gears without proper maintenance. Changing the gear oil can be done at home without the expense of having it done by a professional mechanic. Having an owner's manual handy is a good idea, both for purchasing the right lubricant for the vehicle and to torque the bolts down correctly when finished.
Jack up the car and place two jack stands under the front and two at the back, or drive it onto automobile ramps and securely set the parking brake. Place a drip pan underneath the differential housing near the rear of the car.
Loosen the fill plug bolt on the passenger side of the differential housing using a 10 mm hex socket and an extension, if necessary. Remove the plug and pry the washer from the plug using a flat-head screwdriver. Discard the washer. Wipe the plug well with a clean rag or towel to remove fluid and any fine metal shavings. Set a new washer in place and set aside the plug.
Locate and remove the drain plug at the center rear of the differential housing. Allow the fluid to drain into the drip pan. Remove and discard the washer and clean the plug with a rag or towel. Slide a new washer on the plug. Replace the drain plug and torque it down to 24 to 26 foot-pounds.
Fill a fluid pump with oil and insert the hose end into the fill hole. Pump the fluid into the differential, refilling the pump as needed. Stop the filling process when the fluid begins to overflow the hole. Wipe excess oil off the housing and replace the fill plug; torque it to about 26 foot-pounds.
