Bought another 84 4x4 for parts (bargain, and it has great spares) however the owner told me the 4x4 function dosent work.. Ive stuffed around with it a bit.. I cant get it to work either, It's fully engaged ok, everything looks fine... but no 4x4... now where should i start? Would it be the hubs? or maybe a transfer case? I have the spares to replace both... but dont want to waste my time.. anyone got any ideas!? Thanks!

These things use Flinstone-type technology (which works) by chain driving the transfer case. The chain popping is probably the most common cause. The only thing about the hubs is the auto spindle thingy might not be engaging... that would be unusual.

How are you testing its workability? If you have it jacked off the grouund and the front driveshaft is spinning, it won't be the transfer case...

I think it is spinning.. would that be hubs then?

If you have Auto Hubs make sure they are engaged by selecting 4wd and driving forward slowly for a metre or so. You will hear a distinct ratchet sound when they engage. Turn off the engine, select neutral leaving the it in 4wd, engage the handbrake & chock the back wheels.
Now, if you jack up the front of the vehicle so both front wheels are clear of the ground. Remember safety…
If you turn one of the front wheels by hand you should see the opposite wheel spin in the other direction, front diff in not lsd. If it doesn’t it could be the axle splines, front diff or hubs.
If it does spin, check that the front drive shaft is rotating…
If the front drive shaft is spinning, then put the gearbox into 1st gear. You should not be able to turn the front wheel now because they are being locked by the rear wheels. If they do turn… it is more than likely the transfer case, maybe the chain…
Trick is also to make sure your Auto Hubs engage. Try driving on a grassed area so you won’t lock the diff. Select 4wd and drive forward for a few (5) metres. Then select 2wd and reverse for a few (5) metres. You should here a definite ratchet and click coming from the front axles when you reverse as the hubs disengage.
It’s also handy to remember to reverse a few metres whenever you disengage 4wd to allow the front axles to free wheel. Save spinning a few kilos of metal for nothing.
These things are normally pretty bullet proof, it would be unusual for something to break and you not hear it go BANG.
Hope this helps.