Clutch Smell, Etc

[jd99gst]

I've searched through most of the other threads on the subject, but haven't found anything that was exactly the same.

If I rev my engine in 1st with the clutch down, horrible brake fluid smell.
If I rev it in neutral, clutch down or no, is fine.

I've read that many people have their gears slip, though unless that means the car puts itself back in neutral, I have no idea what it means. I've never had anything happen while shifting I would call slipping.

If I downshift into higher rpms (5k+), terrible clunk noise.

Some earlier posts mentioned spider gears, but I have no idea what those are.

Ideas/enlightening information anyone?

 

[jd99gst]

After searching for many days, I have come to the tentative conclusion that it is my differential. My knowledge in this area is completely limited to what I've recently read.

1) If my differential is dead/on the way out, what kind of price am I looking at to get that fixed?

2) If it is NOT the problem, my original question didn't get answered - what IS wrong here?