AUTOMATIC TRANSMISSION

 Due to its complexity and high replacement cost, the conventional epicyclic-geared automatic gearbox is probably the most common component that people mistrust when it comes to claims that its fluid is sealed for life. Apart from providing cooling and lubrication qualities, the automatic transmission fluid delivers the critical hydraulic function that permits the gearbox to work. Yet, it does not last forever. Even natural condensation that occurs within the gearbox in normal use plays a role in compromising the fluid.

ZF advises that: “Over long periods of operation, mechanical wear on the internal components of the transmission can lead to shedding of minute metallic particles. The friction linings in the clutch packs also wear with time, producing dust that is washed into the oil. However, these particulate contaminants are usually collected by a magnet in the transmission sump, or captured by the transmission oil filter, removing them from the circulating oil. Other potential sources of contamination include a leaking oil cooler, or a blocked/ otherwise defective transmission breather, leading to the transmission oil becoming contaminated with water and/or antifreeze, which is likely to cause rapid failure of the transmission.”

An additional consequence for an older gearbox in good condition is the formation of lacquers that are formed as the fluid degrades. As lacquers build within the internal valve body, oil flow is restricted, and the consequences can range from slower reactions, to ‘flare’ (sudden engine RPM rises between gear changes) and a lack of overall operational refinement.

While automatic transmission flushing additives are available, it is almost impossible to drain out most of the fluid from a modern autobox, because much of it remains ‘trapped’ within the sealed torque converter. While you could conduct several DIY drains and refills to get around this, it can be very time consuming and you might wish to engage a professional workshop to do the work for you. Realising this, EDT has introduced its own automatic transmission fluid change machine, which the company claims replaces up to 98% of the fluid. You can also seek a garage with a Wynn’s TRANSERVE machine. The main difference between these two offerings is that EDT introduces 150% of the gearbox’s fluid capacity, whereas TRANSERVE uses two litres extra fluid, regardless of transmission size.