Hi guys!

I would just like to ask if it is possible to convert my 2nd gen montero equipped with the 4d56t from 2wd to 4wd? If so, what parts would I need to purchase and what modifications do I need to successfully do so. In addition to that, I would also like to ask if the computer box would also be needed to be replaced and what sensors do I also need to replace to make it work. I'm asking here since there's not a lot of information on the net about this and I was hoping someone can shed some light! Thank you in advance!!

Side note: I don't want to get rid of my current montero for a 4wd one due to its sentimental value for me

 

I'm sure it is doable, just a matter of cost and some luck finding the parts. I'd be hunting junk yards for the parts for this project, or buy a donor from which you csn pull all the needed pieces.
At the minimum you will need the following:
Transfer case
Front driveshaft
New (shorter) rear driveshaft. You might be able to shorten the one you have by a computer drive line shop
Front differential/axle assembly
I dont recall if Gen2 has a solid front end, if not you'll need 2 front half-axles
Possibly new front hubs made for 4WD

Do not know what you'll need for controling the transfer case. Did they make them manual with locking hubs option? That might be the simplest way to go. Anything vacuum or electronically controlled will be harder. Not impossible, just harder.
Let us know if you get going on this. Will be fun to follow along.