I bought this truck 5 months ago and have had the same area welded twice now. Its cracking at the cross member welds on the frame rails. Whats causing it? It also has a 6"-5" lift and sits on 35" tires.

 

I had a 85 4x4 150 that did this but it was by the power steering box.I finally got it fixed righj by a good welder.It olny took about 10 times the last time the guy put plates in.

 

An expert weld should take care of the cracks. Especially since it is so new.

 

You coul drill a hole at the end of the crack to prevent further cracking, then grind the crack slightly into a V and preheat it to somewhere around 250 deg and weld it up. If you're not confident about doing this yourself better ask a reputable welder.