For earlier Pathfinder model years (2005-2008), a defect in the radiator allows engine coolant to leak into the transmission. However this defect doesn't appear to affect Pathfinders from 2009 & later. Nissan did include the 2009-2010 models when they extended their radiator warranty on 2005-2010 Pathfinders to 8 years/80,000 miles in response to the transmission defect.
