Terrible transmission Noise

[CountryMan85]

I put a transmission in from a truck that had a bad motor but, from what the guy said, a good transmission. After inspecting it, we put it in along with new clutch, pressure plate, throwout bearin and pilot bearing. After about 300 miles, it began to whine. No big deal. But lately, the sound has gotten extremely bad and sounds like metal rubbing together without any lubricant. Checked gear oil and it was full. Not sure what it is or what I should do. Transfer case might need fluid or something? I don't know, just need some help.

[PEZi]

If it was all fine upon initial installation, I'd worry that it was something that you may have installed improperly. That doesn't mean, of course, that it isn't the transmission... but it would seem odd that you'd get a "good" transmission that functions fine for you at first to suddenly fail. Could it be anything else in the drive-line?