Just picked up an 84 d50. Truck runs pretty good but I cant get the 4wd to engage. When the shifter is in 2wd I can spin the front drive shaft, and when its in 4 hi or 4 lo I cant spin the driveshaft. So, I assume the shifter and transfer case is working. im not really sure how auto locking hubs work, but I assume its not engaging at the hub. im thinking about just buying manual hubs and see if that works? any help is appreciated. Thanks, Jeremy.