Quote Originally Posted by tlefire View Post
The Risk: Sludge Disruption
The "Myth": For high-mileage or neglected transmissions, the old, dirty fluid contains friction-modifying deposits that help worn internal parts (bands/clutches) work.
The Danger: A powerful flush can dislodge these deposits, sending chunks through the valve body and clogging passages, leading to transmission failure.
"A powerful flush can dislodge these deposits, sending chunks through the valve body and clogging passages, leading to transmission failure." quote, tlefire

The top reason why tranny shops want you to do it! JMO!!