> I'm not really certain how this 4WD system works but it seems to me as
> though the dash switch engages the hubs and the transfer case --
> right? *If I put in the manual hubs, what do I do to engage the 4Wd,
> other than engaging the hubs -- do I still need to use the dash switch
> and, if so, how do I know it's doing what it's supposed to do.


A manual shifting 4x4 system, also known as part-time 4x4, uses a
selectable transfer case to send power to the front axle. Most of
these transfer cases also have a Low Range gear for extreme
conditions. When the transfer case is engaged the front drive shaft
and axle shafts are receiving power from the engine. The hubs on the
wheels are there to allow for the wheel to be disengaged from the axle
shafts. If the hubs were not present then axles would turn with the
wheels all of the time, even when the transfer case is disengaged and
no engine power is being sent to the front axles. This would wear out
bearings and joints and also would cause poor fuel economy. By having
unlocking wheel hubs, the wheels can turn freely when in 4x2 mode and
then all of the front axles will remain still.

With automatic front hubs like your Mazda, when you select 4x4 mode,
the vacuum line engages the hub and locks the wheel to the axle so it
can receive engine torque. When you go back to 4x2, in many older
vehicles, you have to reverse the truck a certain distance to
"unscrew" the locked hubs. Your truck manual will describe if this is
required and what distance to reverse.

With manual hubs it requires you to get out and twist the hub by hand
to lock and unlock them. If you are stuck it is not pleasant to
trudge through mud to get to the wheels....so lock them before going
off-road. Then all you have to do is use the internal selector to
engage the 4x4. But, don't forget to unlock them when you are back on
the highway. Manual hubs also have the added benefit of allowing the
use of Low-Range with only the rear wheels powered. If you select the
4x4 Low Range but do not lock the front hubs you get a 2WD Low Range.
Max speed is usually 30mph or slower for low range so it would not be
advisable to drive around this way. You could use it to pull a heavy
load up a hill on pavement where it is bad to drive with the front
wheels powered.

Hope the long explanation helps.
OzarkMtbr