Well my truck sags on the drivers side, but that's because the moron who installed the springs didnt bother to add the spacer atop the drivers perch, as most springs are built the same height but if you look on our axles, the passengers side spring perch is a bit higher then the drivers side.
But yours is sag'n on the passengers side, then maybe just the springs are getting flat. If your truck has the spacer on the drivers side spring, then remove it and maybe that will help level it out.
BigMike
