Quentin Willson's guide to Changing and Topping up Gearbox Oil
Carmakers say that modern gearboxes don’t need oil changes at all and will last the life of the car. There’s not much you can do yourself at home, but if you want your gearbox to really last as long as possible I’d recommend changing the oil every 50,000 miles. Take your car to your garage or fast fit centre and ask them to drain the oil and replace it with the appropriate Castrol gear oil. The whole job should cost less than £50 (check) and will prolong the life of the gearbox and make it feel smoother. While you’re at it ask them to change the axle oil too if you’ve got a rear wheel drive or four wheel drive vehicle.
Checking and Topping up Automatic Gearbox FluidAutomatic gearboxes need a fluid check every month. But beware because it’s not just as simple as pulling out the transmission dipstick and having a quick look. Some cars have different ways to the check the level, including having to have the engine running, so it’s important to look in the handbook and follow the recommended stages carefully. Commonly the procedure will be something like: park the car on level ground, with the engine and gearbox warm, put the handbrake firmly on and move the selector between Park and Drive several times. Some cars need the level checking in Neutral and some in Park. Pull out the gearbox dipstick, (don’t confuse it with the engine oil dipstick) wipe it with a clean rag, push it back home and then pull it out again. Check the reading against the marks on the stick and if it’s low, top up with fresh fluid through the dipstick hole. This can be a bit fiddly and you’ll definitely need a funnel. Do it a little at a time and keep moving the selector to make sure the level on the dipstick is accurate. Make sure you’re topping up with the right fluid for your car because the wrong fluid can badly affect the smooth operation of the gearbox. Castrol do a range of transmission fluids to suit most cars, but note that some modern vehicles need specialised transmission fluids that are only available from a dealer.
The fluid should be a clear red colour and if it’s dirty or particularly smelly, you could have problems with the torque converter. Changing the fluid isn’t expensive and it’s another job that will extend the life of your car that a fast fit centre can do quickly and cheaply. And if the gearbox has a filter, ask them to change that too. As a precaution I’d change the transmission fluid every 50,000 miles.