From what I've read recently when you wire into PTO to get the 1200rpm's the torque converter locks up in the transmission torque converter thinking the trans will be working. That is on the 08's.
I don't think the trans torque converter locks up wired for the 900rpm option. I forget what they call that one.
The question is what will this do to the transmission idleing for long periods of time..I assume it puts wear on it normally not had at regular idle.
2011 F350 6.7 Lariet Premium 3.55 locking, DK.Blue/Silver CC Short Box SRW. Auto,Supplemental Heater, Fisher 8ft HD, 8.5 x 15 ft Ultility trailer for work, Lance 820 for when I can get away.