That nut and washer carry a Cummins part number. Nut is 3903738 and washer 3920393. Another source for parts would be Case industrial equipment. Case part number for the nut is 17043231 (old part number was J903738) and the washer is 892-11014. Many of their skid steers, backhoes, etc had the 4bt engine. Might find it also at a Dodge dealer but don't know the Mopar part numbers. The National Stock Number for the nut is 5310-01-268-8985. Cummins price for the nut is kind of scary at around $20 where Case charges around $1.