I'm new to the 4Runner World (obviously by the question). When shifting between 2WD & 4WD high range, is it nessicary to lock the front hubs for the 4WD high range to operate properly?

 

Yes, they must be locked to have 4wd otherwise you have 2wd...
It is safe to put it in 4hi or 4lo without the front hubs locked, you won't hurt anything, but you will only have 2wd with a lower ratio.

 

one important note on the 4hi/4low shifting WITHOUT the front hubs locked in....

you MUST be stopped to do so, else much grinding happens.

WIth the front hubs locked in you can freely shift between 2hi and 4hi "on the fly"

its still advisiable to come to a complete stop before shifting to 4low in any case.

 

They dont have auto locking Hubs?

 

My 89 did have autohubs. you could move the lever below like 30mph or something. I don't think there are too many functional autohubs are still out there. Most have been ditched for manuals by now.

 

SR5 had autos and DLX's had manuals in 89 I believe.

Since you say your new to the 4wd stuff, I'll throw this out there too. Don't use 4WD on pavement. You can hurt your transfer case.