truck stuck in 4x4

[MitchMan]

when i got my 98 z71 the 4 hi light always blinked. even if 2 hi light was steadily on or 4 lo. while going down the road I accidently hit either my 2hi or 4 hi doing 40-50 mph. The truck skidded and I heard a grinding type sound. could only stay in 4 hi or 4 lo after that. so I was towed to a repair place and they said a fork was bent in the transfer case, and I removed the front shaft so I could drive it until repairs. I have put a used and warrantied transfer case in and the problem remains. any ideas how I might fix? thanks in advance