The ring can be removed and transferred to the new axle, but it is fussy to remove. Use a torch to heat the ring, but not so hot it changes color and pound the differential end of the axle on a block of wood on the floor. Get it to move enough to use a bearing puller to work it the rest of the way off. Wear a glove or only grab the axle by the flange. You don't want the hot tone ring to land on top of your hand.
The tone ring axles were used in all 4-door Blazers, Jimmy and Bravada from 1990-1992. Remember that 4X4 axles are longer than 2WD axles. The tone rings were never used in 2-door or pick-ups other than the Syclone and Typhoon. The tone rings were not used in S-series beginning with the change to 3-sensor ABS systems.