so just completed swapping a 4R75E from a 2008 4.6 4X4 into my 2000 5.4 4X4, and am having issues. the transmission will shift through the gears from park, but when you shift back through and try to put it back into park it grinds and will not go into park. there is also no power in any of the gears. the truck starts fine and is not shooting any codes. and i have a custom tune to account for the different OSS counts. and when filling, i filled 9qts, started the truck and shifted through the gears, turned it off then filled the remaining 4.9qts. and it did grind that time as well. could it have anything to do with the Transfercase? it sounds like a control/fluid issue to me though. i was thinking torque converter. ANY and ALL input is appreciated. i need this thing back on the road ASAP, i have drill this weekend PLUS its COLD OUT . if i missed anything let me know.

ALSO, the donor trans has a VSS sensor, my old trans did not. we came to the conclusion that would not be an issue. was i wrong?