Rear pinion nut came off, causes?

My rear pinion nut came loose and the drive shaft fell out of my 02 Dodge Ram 1500 while I was driving. Luckily I heard the whining and pulled over before the shaft dropped, so no damages any where. The yolk is still attached to the U joints which are in great shape. I have not had my truck worked on by anyone. I can replace the shaft and nut and take it to my mechanic to get the proper torc. Question is, is therr something wrong in my rear differential that wpuld cause this? Thanks in advance for your time.20190428_193517|690x387

I know your RAM is a 2002. But guess what.



Well that could potentially be good news that my differential isn’t at fault and may not need to be replaced… potentially. Thank you @Tester

If your truck is included in the recall, repairs should be free.