The transmission fluid change is the tried-and-true process that your owner’s manual specifies when it calls for a transmission service. Your mechanic drains the transmission fluid, replaces the filter, then refills the transmission with fresh, new fluid. The transmission fluid change lets your mechanic get a close look at the transmission pan and the filter. This can reveal the presence of metal particles or other debris, which can indicate a bigger problem that needs to be fixed before it gets worse. This makes the fluid change an ideal preventive maintenance procedure. The transmission flush process uses a machine to replace an automatic transmission’s fluid. Many auto repair shops own these expensive machines. The old fluid, dirt and sludge is pushed out under pressure, and new fluid replaces it. Flushing usually costs significantly more than a fluid change, due to the cost of the machine. Many shops tend to price the procedure for high profits.