Transmission making 'sounds'
 

So, I'm on my drive home from work today and I'm on the highway. I shift into 5th at a moderately low RPM, probably around 4k, if not less. About a minute later, all of the sound there's this awful grinding/metal-rubbing-on-metal sound screaming from, at the moment, what I thought was the engine. Immediately, I drop her into neutral and pull of the highway. As soon as I hit neutral and pull it out of gear position, the sound went away. Just to check to make sure, I popped the hood and checked for any anomalies and couldn't find any.

I proceed back down the highway, and get ready to shift into fifth. Almost immediately after putting it into position, but not even releasing the clutch, the sound starts again. I immediately pull it back into 4th and continue the drive home in 4th.

I got her home and changed the transmission fluid. The fluid had a lot of brass-esque (i.e. were not silver) shavings. I'm not sure when the fluid was last changed and the car just rolled over to 156k.

Before changing the fluid, at some points I thought I heard something moving around in the box, while the car was in neutral and braking to a stop.

So as it stands, I cannot shift into 5th without experiencing the worst sound ever. 1-4 and reverse all seem to work with no problems. Any thoughts? Is it worth fixing, or just replacing with another tranny?

i'd just replace it with another. i mean it's not like they're hard to find.