How to perform a transmission oil change

If you drive an automatic car, there is a tendency to ignore that most technical of components, the gearbox. Performing an automatic transmission flush and oil change is not as daunting as it seems, although it is a little more than a simple auto maintenance. Here is an easy-to-follow guide to help you service most auto boxes.

Preparation

The first thing which you need to do is to ascertain if your transmission needs servicing. In basic terms, this amounts to "how to check the oil". Most manufacturers state that the gearbox need to be "at operating temperature". This doesn't mean the engine temperature, so a drive of around 15 minutes will be needed. Park the car up on level ground and, with the engine running and foot brake applied, move the gear lever through all positions at least twice. Turn off the engine and, under the bonnet, remove the oil dipstick, wipe, replace, remove and recheck that the level is within the "hot" markings. Whilst there, check the condition of the oil. A reddish colour is good, brown is not. This is a better indicator of servicing needs than mileage or age.

Tools and parts

The tools needed for a transmission fluid change are a drain pan of sufficient volume for the waste oil, ramps (or a trolley jack and axle stands) and a spanner suitable for removing the drain plug. If you are completing a full service, then you will also need the appropriate sockets to remove the sump and transmission filter. Your local motor factor should be able to identify the correct automatic transmission (atf) fluid for your vehicle.

The oil change

- When the transmission has been fully warmed up, park the car on level ground and either raise it on axle stands or run it onto ramps in order to access the underside of the vehicle. - Place the pan under the transmission drain point, and remove the plug, being careful of the hot oil as it flows out. - Leave the fluid to drain for 15 minutes. At this point, if you are replacing the filter, you need to remove the sump, detach and replace the filter, and replace the sump with a new gasket. - Replace the sump plug, with a new washer in necessary. If performing a flush, refill with flushing fluid and repeat the previous steps. - Refill the transmission through the dipstick tube with fresh ATF to the "cold" level. - Run the car, check for leaks and perform an oil level check, adding more fluid if necessary.