Rules Of Cleanliness When Working On Automatic Transmissions

Thoroughly clean connecting points and the area around them before separating.
Place parts that have been removed on a clean surface and cover them. Use paper or foil. Do not use rags that can leave lint.
Carefully cover or close components that have been opened if repair will not be done immediately.
Install only clean parts. Only remove replacement parts from packaging when they are ready to be installed.
Always replace O-rings, sealing rings and gaskets.
Lubricate O-rings with ATF or Vaseline when installing to prevent tearing them during assembly.
Lightly lubricate sealing rings on the outside and on the sealing lip with Vaseline.
As a general rule, do not use any other lubricants for parts coming in contact with ATF, otherwise the hydraulic function of the transmission will be impaired.
After installation of transmission, check ATF level and top up if necessary.