Gear oil is essential to maintaining your transmission. The oil keeps the gears cool as they work to move your car, and it makes shifting easier and smoother. You need to maintain the level of gear oil according to your manufacturer's reccommendation to avoid problems with your transmission. Cars like a Toyota Celica are easy to maintain because of the way they were designed. You can fill the gearbox oil on a Celica quickly and easily.
Open the bonnet of your Toyota Celica. Stand on the driver's side of the car and look down at the transmission, just behind where it flares to the flywheel housing. You should see the speedometer cable connecting into the transmission near this area. Look in front of this cable connection about 6 inches (toward the engine block), and you will see an Allen head bolt protruding from the transmission case. This bolt is the fill plug for your gear box.
Remove the gear box fill plug by using an Allen wrench to turn it counterclockwise until you can pull it out of the transmission case.
Attach a 2-foot rubber hose to the bottom of a funnel with a hose clamp. Tighten the hose clamp with a flathead screwdriver by turning the hose clap screw clockwise.
Put the end of the hose into the fill plug hole of the gear box. Hold the funnel up so the hose runs in a straight line down into the gear box.
Slowly pour 75/90 weight gear oil into the funnel. A Toyota Celica only takes 2 to 4 litres of gear oil, so check the level in your gear box to make sure you do not overfill it.
Change your gear oil after heavy driving, long distance driving and on a regular maintenance schedule. Gear oil loses its viscosity quickly under high stress situations, and even though you may have enough oil in your gear box, it may not be doing any thing to protect your gears.
Maintain the recommended levels of gear oil in your Celica, or you will cause damage to your transmission that will require it to be rebuilt or replaced.