It's like a fish! It's fine in the water, but if you take it out it will die
But seriously, umm.. I realise that you have probably checked already, but you should make sure that the cables are plugged in properly. And i'm no expert, but could it be a fuse that has blown that is causing the inability of the drive to sustain speed.
Also, is there any possibility of the drive itself being damaged when you took it out?
I think the DVD drive is brocken now. Or something damaged when you removed it. You should check where is the problem first. If you cannot fix it, you may need to buy a new one. How long do you hold it? Is it a new one?