I posted about a week ago that my 8420 was having hydraulic problems.  I got it at dealer and they are having a difficult time getting it to throw code.  I had it configured on planter as such: it uses a case drain for motor return, Power beyond=variable rate drive, scv 1=vac 1, scv 2=vac 2, scv 3=lift circuit (planter tech confirmed i had everything hooked up correctly).  i've been running planter on 9320 same way with no issues at all, but I would really like to get planter back on 8420 asap.  the 8420 would run the planter for about 5-8 minutes and eventually throw the low clean oil reservoir code and shut hydraulics down.  to my knowledge, there are no flow issues what so ever, aka when it runs, it runs the planter wonderful.  They flow rated everything and couldn't get it to throw anything at all.  when the tech was out the other day we got it to throw code while sitting there running everything on the planter for 10 minutes and accidentally hitting joystick for loader that are on scv 4&5...last fall we ran tractor on air seeder over 600 acres of WW and had no issues at all...i guess i should sit back and see what they figure out, but i don't wanna just throw parts at it and hope for the best.