on an item like a transmission a scrapped item is a gamble. I personally bought items that didnt have burnt out ATF in them (check in the diff oil seal area etc).
BUT
I still tore them down to repair them with soft parts or atleast get the VB perfectly smooth n nice before the box goes in the car. On any Transmission job always blow out the cooler line in the radiator with something, even plain ATF mixed in petrol and blown gently backwards cleans it out but it is vital to blow it again in the right path to exhaust all petrol/solvent from the cooler.
This practice is mandatory because the cooler in radiator of modern cars can trap debris like a filter too and can quickly kill a gearbox from being clogged.
Its best to find a good mechanic that can get you a clean item from scrapyard as they can command their choice there unlike walking customer.
