Transmission service performed properly by qualified transmission technicians will never damage an automatic transmission. Though some believe that a service to your transmission will ruin it. This is because of some type of cause-and-effect between transmission flush and transmission failing. The two often seem to occur at about the same time. This is because far too many car owners only consider having transmissions serviced after they've noticed a problem with its performance. At this point the transmission is already damaged, so they're hoping to fix the problems with a transmission service. A transmission service is a maintenance job that's supposed to be done while the transmission is working properly to avoid later problems. Though depending on what's causing the problem transmission service can sometimes save the transmission. The best way to avoid the damage caused by fluid shear is to ahve the fluid changed regularly, before you notice a problem with the transmission's operation. Once you start to feel a problem it may be too late.