Transmission and Cylinder 7

My 2007 Suburban LTZ recently started to shift very hard. Went to Autozone and the
computer returned cylinder 7 was misfiring. The vehicle is close to 200,000 miles so I
went ahead and replaced all the plugs and wires. This didn't fix the problem so I
replaced the coil pack too. This didn't work so I took it to a transmission shop. They ran
a diagnostic and recommended a total rebuild. So I had them do that. Guess what! That
didn't work either. They also repaired the rear main seal at the time.

After a computer reset the vehicle runs fine for a minute or two, then the check engine
light comes back on and the problems begin again. As he explained it, for some reason
the sending unit is calling for a pressure increase in the transmission and that leads to
heavy shifting. The computer is still saying there is a problem with Cylinder 7 misfiring
as well. I am probably coming close to spending what it would cost to put in a crate
engine and we still have no solutions.