You don't use the plastic bushing with pressure lube. Take the top off again, slide the shift collar in HIGH range and stick a good  length screw driver between the end of the coupler that is splined on the shaft and the low range gear and see how much movement you have. Also are you sure the snap ring on the inside of the gear has firmly seeded? I have seen them wear the groove on the shaft  and then things move around on the shaft. Send me a phone number. John