pull to the left in 4wd

[captain_chaos]

Now I've got my truck running after about 3 years of standing idle i decided to see if it moves. Well I'm pleased to say the truck rolls under its own power and stops luckily lol. Now during one trip along the lane i engaged the 4wd to see what happens. All the parts click and you can feel that it has engaged. However the truck then really wants to pull to the left as if the front passenger side wheel has locked. Any suggestions as to what's causing this, and to fix it? I'm only assuming that because it's been stood for years that something has probably seized up.

[wishbone]

might be the ADD selector fork not working properly (vacuum lines to diff)

I'm pretty sure this would mean only one front wheel getting drive, just not sure which one..

have a read of this.