S40 Return line on auto transmission

[Ed]

Hi,

I want to change my transmission fluid. The instructions I have say
drain the transmission and refill with 2 liters of fluid. Then undo
the return line from the cooler to the transmission
and connect a hose to a bucket and run the motor on idle and so on.

The problem I have is deternining which one is the return line. Both
have a rubber hose. One tube come from the bottom of the
transmission. Not sure where the other goes yet.

Thanks,
Ed