Replaced and installed new CV axle, first axle failed shifting from 2WD to 4WD HI. New axle passed road test with flying colors, wanted to try out the 4WD, shifted from 2WD to 4WD, the new one failed

Did you replace them yourself? there is a spring 'c' clip that must be in place before attemting to seat them properly. If you can pull the axle back out without using a prybar, the axles haven't been seated properly...worst case the spring is weak, when you pull the axle back out, the spring is left behind to play hell with the gears in there...should have been a forty five minute job, now bust out the telecoping magnet and go fishin'...anyways a common mistake is to not seat the axles properly with a proper retaining (not weak) C clip. Think maybe yours need to be shoved in more till seated properly or the retaining clips looked at for looseness.