G,day matey am i looking at these pics the right way. if you were to grab two lengths of steel, same type of profile but a lighter guage,now bend one up and down to simulate roughly what has been discused, to the point of fatigue. now bend the other in a swaying motion,till it too reaches the point of fatigue. which piece looks like you chassis rail. could i be right in saying that MAYBEE just maybee that the trailer has shaken the crap out of the rear of the ute, with a swaying motion .give hayman reece in Dandenong a call,i remember that they have a simulation test for this very same thing, not they will tell you ?? . if i get the time today i will go down and see a bloke who knows of this of this tale(do not want to get him in trouble) but i seem to remember a story of this sway test on a ute that could of been made in broadmeadows ,doing the exact same thing cheers Graham