A critical function during transmission repair is flushing the cooler lines and radiator tank. This is done not only to clean the system but also to verify flow. For years this was a relatively simple process however, more recently it has become more difficult due to thermal element assemblies as well as transmission fluid warmers.
Before flushing a system be aware of any obstacles or restrictions to ensure that the whole system is flushed completely. Forward and backward flushing is preferable.