A new shift motor assembly is most likely in good shape. There is also the possibility that the internal gears are worn from too many missed shifts and they disengage on a hard pull. Unfortunately, it takes a full teardown to inspect those parts. There is a sliding gear that either engages a planetary gearset for low range, or shifts to direct drive for high. There's no way to see those parts with the rear end assembled.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!