I've got some rear suspension problems...

[Phoax]

Thanks for the replies. The other side isn't rusted out at all. It's a flatbed with nothing protecting the rear suspension from the wind so maybe it was parked for a long time with the one side getting blasted by salt wind. I'll do some more inspection but I've done a lot of work on the front half of the truck and haven't seen anything alarming so I think that is probably the worst spot.