Recently had a bad humming noise from front end. Front hub assembly was
shot. Easy job and torqued to spec. Now both have been replaced.  Have 206k
Kms (~125k miles) on now.

Now I'm getting a humming noise that varies with the speed of the vehicle.
Usually starts around 25mph and varies right up to highway speed.

Strange thing is, the hum definitely changes with speed, if I throw it into
4wd Auto (it's a'95) from 2wd the hum changes it's tone (holding speed/rpm
steady).  It still varies with speed but at a different freq.  If I switch
back to 2wd it switches back to original tone (cruise holding speed/rpm
steady).  I'm ruling out the hub I replaced because of this freq. change at
constant speed.  Also tire hum wouldn't exibit this behavior.

Can this be u-joints on front drive shaft?  Front CV's? I hate to guess the
xfr case has a bearing problem...

All help appreciated,
Chuck.