1997 f150- broke a fork in the transfer case
 

I got a 1997 f150 4.6 4x4 with the bw 4406 transfer case, noticed a grinding noise on the way to work went to pull over to check it out and it kicked out of gear, only way i could get it to move was 4 hi so i got it back to the house and pulled the tcase and noticed it broke a fork inside of the tcase and shot the pump, so i got another tcase put it in same thing happened.... Any ideas on what could be causing this....???