misfire I have a stock 2015 GMC Sierra 1500 Denal1 with a 6.2 and 8 speed transmission.
Codes P0711, P0700, P0304, P0300. Anyone know if there is a correlation between the misfire code and the transmission code?

P0300 random misfire detected
P0304 misfire detected cylinder 4
P0700 TCM problem detected
P0711 transmission temperature circuit problem detected

They don't look related.

Did all of these codes set at the same time?

I would check grounds everywhere.

You're right they don't look like they're related. The codes showed up as I had printed here and I deleted two but P0300 and the P0711 were permanent had to take to mechanic. They replaced spark plugs and he thought that there was a connection of the two through a solenoid which he figured that the misfire caused the transmission code to show up. At this point I'm not sure if they are a hundred percent positive they cured it. The problem with these engines and the active fuel management which stops the cylinders from working are causing lifters to stick. GM knows about this and dealerships are selling a chip to plug into OBD port to delete the AFM system so it runs on eight cylinders all the time. Again, not sure if the possible sticky lifters are part of problem too.

It'* a slight possibility that engine problems can set tranny codes but the only time I seen it was when the engine was way bad and it is usually shift codes not temp.

OK. I had tried to take out the spark plug in No. 4 but it seemed awful tight and I stopped when I heard a little click which to me sounded like something turning but almost rusted. They got the plug out with not that much effort and the porcelain was broken. I used a proper spark plug socket but am curious if porcelain was cracked before.

How does it run with the new plug?

I had all spark plugs replaced and according to the code scanner all cylinders did not report a misfire. The truck doesn't seem to run any better, runs rough at an idle and seems to be misfiring while driving although the scanner can't pickup a mechanical fault. Is there something I can use to clean the lifters out. Seafoam maybe?

I wouldn't assume that it'* the lifters just because they're there to be assumed about. Most of these work just fine with AFM never being touched. A real diagnosis is needed.

What is the fuel pressure at idle?

If that thing is missing and your scanner isn't picking anything up tells me that either your scanner or the PCM has a problem.

I personally do not have a scanner but a code reader. And the reader tells me fuel pressure:
at idle after warmup is 44-53psi
constant 1800 rpm is 40-60
at 60 mph is 35-60
increased to 84 after shutdown
dropped after 20 mins 62 is lowest
All ground wires I checked were good