Its over 30 years since I last dismantled a D8H/K final drive, however if my memory hasn't faded too much I believe that outer bearing can be replaced without pulling the outer hub. it is the outer bearing that gets notchy because it only oscillates back and forth with the track frame, the two bearings inside from it actually fully rotate with the bull gear hub. Providing all other bearings are ok you could try replacing the outer bearing and re tension the set.
By the way, what is the serial number of the tractor, there are a series of modifications over time to finals in 46A's bigger inner bearing, larger bull gear and intermediate gear etc as well as different seals.
Wombat