loud whinning noise then big clunks?
 

Just bought 2 Rangers a 93 4x4 running and a 94 Ranger 4x4 for parts, drivetrain is out of the 94. The 93 drives but let off the gas and it would make a grinding/whining noise then a couple loud clunks. the guy we bought them from said it was the trans and to take the 94 trans but keep the 93 transfer case cause the 94 didn't work in low. We change the trans and kept the 93 transfer case, started it and right a way the noise was there and wouldn't move and the noise definitely was coming from the transfer case. Moved it forward then we could shift, got on road and got on it a bit then it all started again like it fell out of gear and then hard knocks like it was trying to grab. Transfer case bad? clutch bad? Driving the sound and feels like right in front of shifter but that can be deceiving but when it was doing it parked and wouldn't move it was for sure the transfer case. Anything would be helpful, Thanks