Auto hubs say on the cover
"Auto locking hubs" or something
to that effect.
Junk the autos, they are weak and troublesome
if the low range works, your T-case is fine,
my best guess is the hubs are sticky, and I
never could figure out how to get those
dumb things apart, hit the wrecking yard
and get a used pair from a Track/Kick or a
Sammy, they interchange
Wild