Dispersed camping on Arizona Trust Land. This is similar to BLM but it does require a $20/year permit. It can be purchased online at: Land.AZ.gov
If you drive far enough down the main dirt road it does change to BLM so no permit required but I haven't explored that far. The area right off the highway has plenty of room to spread out with many spots for any size rig. It's a popular spot for ATV riding. Good cell service.