XC90 D5 Auto gearbox, need advise

[AdventureDriver]

My 2004 XC90 D5 has some automatic transmission problems, erratic changes and overheating and going in limp mode.
So I bought an secondhand box (350 Euro). But it turned out I bought the wrong one, a 55-50SN (front wheel drive) instead of an 55-51SN (AWD).

Now the question, shall I open the two boxes, and move parts over, like the solenoids?

The box in my car has already, by a previous owner, been opened, and holes where drilled in the cover to adjust the solenoids from the outside.

Or shall I bring the second hand transmission back?

Or shall I put the 50SN in and ditch the rear wheel drive part?

[Tannaton]

If the gearbox has been messed about with already - I wouldn't persevere with it.

I don't think you can physically fit the 2WD box as the right hand driveshaft is different and not having powered AWD is bad for a number of reasons - the electronic traction control and stability control systems don't work as intended.

It is possible to put the guts from a 2WD 50 variant into a AWD 51 - there is a thread on here where someone has done that - but you need to know exactly what you are doing...

Your lowest risk bet is send the second box back, get someone to look at yours who knows how to repair them....