Transmission shifting issues jumping out of gear while driving?

I recently started having shifting issues with my van with jumping out of gear while driving and not wanting to go after stopping. It would rev up and jump back into gear or rev up several hundred rpms when trying to shift. It then went into limp mode. I had someone tell me that its most likely the trans solenoid. I guess a common issue on these vans especially with high miles. It also has a loud buzzing sound if you will. It sounds very similar to a power steering pump low on fluid. I ended up replacing the trans solenoid and the input and output shaft sensors based on the codes. I don't have them anymore. After replacing a these parts, on my initial test drive all seemed great. Drove about 20 min then stopped at a store but once I started out again, all the symptoms came right back. I ended up in limp mode again. Codes on that trip were; P0700, P0732, P0871, P734. I am at a loss. I mean, I guess I could have bad parts right out of the box. I went with the cheaper china parts because the van isn't worth much. Any help is greatly appreciated!