During this investigation, ODI identified 29 reports of cracked and/or fractured hitch receiver assemblies installed on the subject vehicles.The majority (27 of 29) of the reported hitch incidents occurred prior to the initiation of PE10-048 in December, 2010.This investigation has been characterized by (1) Scant forensic samples available for inspection and review since most of the reported incidents occurred prior to ODI?s investigation and pertinent material has been scrapped; (2) Uncertainty regarding the contributory role of issues such as unintended hitch contact with road surfaces, use of hitches with offsets that exceed Winnebago recommendations; and (3) Other usage factors.Based on reported failures, the indicated failure rate for detected and reported cracking /fracture incidents associated with the estimated population of subject vehicles was found to be 0.10% after the vehicles had been in service for between 6 and 8 years.Reports were higher in calendar year 2007 (9 reports) than in succeeding years 2008-2010 (3-5 reports per year) and 2011 (2 reports) and appear likely to decline further due to diminished use associated with vehicle aging.ODI is aware of only one consumer complaint (ODI# 10368002) in its files describing a hitch receiver malfunction in Winnebago-Itasca vehicles.As of September 2013, Winnebago has reported that there have been no additional incidents of cracked or fractured hitch receivers reported since the most recent incident reported in May 2011.A safety-related defect has not been identified at this time and further use of agency resources does not appear to be warranted.Accordingly, this investigation is closed.The closing of this investigation does not constitute a finding by NHTSA that a safety-related defect does not exist.The agency will take further action if warranted by the circumstances.For more detailed information, see the attached closing report.