I'm just weighing up the options of free wheeling hubs vs ADD.

I am thinking about replacing the std 4.88 diffs on my GV with 5.125 diff centres (bigger tyres and want airlocker) and free wheeling hubs from the wreckers, but I also noticed they have an ADD front diff centre as well.

Now, what are the pros/cons of free wheeling hubs over ADD?

Pros:
- More reliable - one less thing to break namely the little penumatic compressor
- Less wear and tear in the front diff as it is not running permanently
-

Cons:
- A bit more inconvenient - have to get out to engage the hubs
-

Cheers

Freewheeling/manual hubs have been discussed at length in this thread:
http://www.zukiworld.com/forum/index.php?topic=7846.0

There is a bit of debate over how userful they are and some people have had problems with wheel bearings wearing out quickly and they think it is because of the maual hubs.  Anyway that is a good place to start.

One thing I will say is that installing manual hubs won't get rid of the current penumatic shift on the fly 4wd engagement, it will only mean that the drive shafts won't be spinning all the time.  When the hubs are lock that car will be exactly the same as it is now and you will be able to shift on the fly, if they are not locked then you can't but you will be putting less wear on the cv's.

I am going to run a fully open front diff, with a Vitara diff which doesn't have ADD. I don't see any difference when running locked free wheeling hubs but still in 2H. I can still effectively "shift on the fly", I just need to remember to lock the hubs when I air down and only engage 4H/4L as required from inside the cabin.

I am going to run a fully open front diff, with a Vitara diff which doesn't have ADD. I don't see any difference when running locked free wheeling hubs but still in 2H. I can still effectively "shift on the fly", I just need to remember to lock the hubs when I air down and only engage 4H/4L as required from inside the cabin.

You can certainly do that.  The setup you will have is essentially the same as my X-90. Once I have locked the auto hubs, I can shift on the move between 2H and 4H, but not, of course, between 4H and 4L.