Hi.
I have a 1993 2.4 petrol with auto locking hubs. I put it into 4wd hi and go in reverse to lock the hubs for a metre
then when I go back to 2wd,I drive forward to unlock the hubs.
This is from my Vauxhall Frontera driver's manual:-
Automatic locking hubs:-
To lock the automatic free-wheeling front hubs into the drive position,stop the vehicle and
shift the transfer case lever to 4H or 4L or 2H. When the vehicle is started again the hubs will lock
automatically.
Note:-
Once the hubs have been locked,they will remain locked even if the transfer case shift lever is shifted
from 4H or 4L or 2H whilst the vehicle travels in the same direction. To unlock the hubs,stop the vehicle
and shift the transfer case lever to 2H,then drive the vehicle slowly in the opposite direction to which it had
previously been used for approximately one metre.
Note:-
When the vehicle is in 4H or 4L,hubs will temporarily free and re-engage when vehicle changes direction.
I hope this is helpful. There is more info in my owners manual.
R.I.P Sable!(2005 to 2013)