99BC 873leaked all gear oil after washing out belly

I am in need of advice where to locate the cause of leak purchased this machine 1/29/16 went straight to carwash and sprayed off exterior and then proceeded to spray the mud out from what i am calling the belly there is an inspection cover off and was spraying in through that access and the water and debris was not draining so with it being on trailer still i had easy access to the drain holes underneath at the rear and i sprayed to clear the hole and then put wand further in to clear out and seconds later it proceeded to leaking all the chain case or gear oil out any ideas

99BC 873leaked all gear oil after washing out belly