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can you tell me what year this is ?
and nothing has been done to the transmission that this problem just started this problem after work was done?
Probably several different people has topped up or changed the transmission oil and as far as I can recall the owner even has done it himself.
The model is a 2002 Freelander td4.
ok the only thing that will cause transmission fluid to spill out the breather valve would be wrong fluid, over filled fluid, under filled fluid OR the fluid getting too hot and boiling
the best course of action is to have a flush performed to the transmission where they connect a machine and remove all the old fluid and add all new fluid and make sure the fluid is exactly full
that is the only way to remove ALL the old fluid and it should clean out the oil cooler
if by chance it does this again there is an internal failure boing out the fluid
but most of the time a good flush and cooler flush will correct this problem