Welcome to the forum
4R44E and 5R44E are pretty much the same transmission internally.
FYI, XX55E were only used with 4.0l engines
Ford added the 5th gear electronically, when trans needs to shifts out of 1st, OD is engaged, this is the "new" 2nd gear
4R44E has these gears: 2.47 / 1.47 / 1.00 / 0.75
5R44E has these gears: 2.47 / 1.87 / 1.47 / 1.00 / 0.75
You can see the "new" 2nd gear ratio inserted, 1.87
1st and OD engaged at the same time:
2.47(1st) X .75(OD) = 1.85(new 2nd), with mechanical transition it comes out as 1.87
Computer added 2nd gear, since computer already had control to engage and disengage OD, it was just a firmware change, and Ford gets a "new" 5-speed
So yes you do need a different ECU to control the 5R44E
ECUs are specific to engine and transmission, also PATS(Fords Anti-theft system)
So you will need 3.0l/5R44E ECU and you will need the Keys for that ECU and have your ignition and doors re-keyed for those keys.
Or after the install have a mobile locksmith come out and add your PATS keys to the new ECU.
ECU must be installed in the vehicle and all wiring working in order to reprogram it, you can't added keys otherwise, not even Ford can do that.
Automatics(and most manuals now) have integrated Bell Housings, can't be removed and changed without total rebuild.
3.0l has a unique block bolt pattern.
So you can only use a transmission from a 3.0l engine, and in your case a 2WD transmission, 4WD won't work and can't be converted without total rebuild.
Since XX55Es were only used with 4.0l engines they won't bolt to a 3.0l engines
Overall I see no benefit in changing from a 4R44E to a 5R44E you don't get more power, maybe if you are pulling a trailer alot the Faux 2nd gear might be helpful in getting started but all the other gear ratios are the same.
You can call a Ford Dealer and ask them if they can change the firmware, that would be a better option than dealing with the PATS system.
But it has to be done IN the vehicle, so you would have to get the vehicle to them, current ECU should work fine with 5R44E, just no 2nd gear, so would be drive-able to get to the Ford Dealer, IF.........it can be given new firmware, which is a question mark.
Since these two transmissions are identical, drive shaft and trans mounts will be the same
31" tires, when you change the tire diameter you change the axle ratio, if you go larger you get better top speed but lose low end "pep"
On the door label will be an AXLE code, get it and look here: http://www.therangerstation.com/tech...le_codes.shtml
Get your axle ratio, 3.73 is the most common
Get stock tire size, on that door label as well
Then go here: http://www.therangerstation.com/tech...ioChange.shtml
Put in new diameter and old, then axle ratio
The lower the number the less "pep" you will have
Look at "new" ratio, thats what you would change to to get back to original ratio
If you have a 3.73 and changed to a 4.10 rear axle then you would get the "pep" back and the speedometer would be correct, bonus, lol.