Really weird transmission problem.

[Jonnyblaze]

Hey guys I did a 5 speed swap on my s13 about 1,000 miles ago and it was just perfect for the first 500 miles. After that it would start to grind when shifting 1-2 at high rpm. It got progressively worse and began to happen in other gears as well. Now it will grind every other time I shift in almost every gear. The weirdest thing is today i revved the car with the clutch down and the shifter in neutral and it was grinding until I released the clutch. When I'm reversing or moving slowly in first and then press the clutch down and leave it in gear it will grind. Any ideas on what the problem is? Input shaft bearing? Throw out bearing? Thanks for the help.