DON'T use std dexron/atf.
Use only Castrol TQ-D, about £9 Litre at Halfords etc, you'll need 2.55 Litres, you can and I have used gear oil 75W90, this will quieten things down, but will/can be be a bit of a pig to change when cold.
There were many variations of the T5 internals, even as supplied to ford for the cossie, so I'd stick with the closest stuff to the original, the TQ-D, unless you have serious wear.
tabetha