Attempted to remove WD My Book from Enclosure and Put In Internal Bay

So, my roommate bought a Mac Pro, which has three internal bays for SATA drives. 

He asked if I thought he could remove the enclosure from his WD 4 TB drive, and just slide it in the bay. I told him I was not 100% positive, that it would be risky and he def needed to backup before trying. So with all that, he asked me to try.

I removed the enclosure and all, and removed the power/logic board. It slid into the bay fine, but then it gave a “drive not readable” error message on the Mac. I thought, uh oh, probably not a good sign. So I immediately pulled it back out, reconnected the logic board, replaced the enclosure, etc., and replugged it back into the USB port externally, but now, it’s giving the same message – “drive not readable”.

What could I have possibly done? And it’s giving two clicks now that it wasn’t giving before. It’ll spin up and then click-click. It shows up in the Mac’s disk utility, but is totally inaccessible. Same thing on my PC, shows up as blacked out drive, but shows 4 TB, shows WD.

Any ideas on how to fix this? Sounds like the head got stuck somehow maybe during the transplant? Anything to try to fix that short of taking off the casing and moving the head as an ultimate last resort? I feel absolutely awful since it was a 4 TB external (like $399!!).

Hi ecceben, sorry to hear you are having problems with your drive, note that removing the hard drive from the enclosure will void the warranty. As you said the hard drive could have been damaged when being moved out of the enclosure. If you don’t need to recover the files from the external drive you can try writing zeros using the Disk Utility app. Check the link below for more information.