Possible that my trans was swapped along with engine swap?

[Airplanemechanic]

I have another thread about fog lamp switches, but this question would be about whether or not my 4.6L swap to a 4.0L included a tyranny swap as well. I'm not versed in Explorers enough to know if the 05 4.8 and 4.0 had similar transmissions. None of the people who would know are still alive or contactable. To my knowledge of power and torque, you would need to change gears at different rpms and a whole mess of mechanical physics if you took it from a 8 cylinder to a 6... but it's ford right?

TL/DR: my transmission has been slipping at cold temps ever since I had to put it into 4w high last week due to icy weather. When I have ever engaged 4WD high or low, I religiously do it at a stop and in N like you're supposed to. I haven't gotten under the truck since, but I'm afraid I may have a leak of tyranny fluid if it is suddenly slipping. I don't hot rod or anything like that, I may have had to goose it out of side streets here and there, but I generally don't abuse the poor thing being that it's just under 250k(it was hinted that the swapped over equipment was about the same mileage as the chassis, and my dad insisted on the instrument cluster being brought over with the engine- so thats indicated engine mileage).
Is this a fluster cuck Frankenstein I should get out from under asap? Or can a simple transmission fluid change/ level check fix my ails?

 

[Fix4Dirt]

as i recall it the bellhoysongs were different. however the rest of the guts afaik were he same, so they couldve put a different trans altogether or just swapped bellhoysong and pcm. afaik at least