I'll describe my tranny's problem and maybe someone can gimme an idea of what's up. 5 speed manual, 88 Camaro 305:

As I'm sure you know, 1st gear is top left, so 1st, 3rd, and 5th are all "up" and 2nd, 4th, and Reverse are all "down."

All three "down" gears are messed up while the three "top" gears are absolutely fine.

4th and Reverse simply grind. With reverse I just slide it into 2nd real quick before Reverse to "reset" everything and then Reverse won't grind. With 4th, if I hold the clutch down and leave it in third for a second or two before putting it into 4th it wont grind, or will grind less. It seems like 4th has to "wind down" to match the speed of the clutch. (f.y.i. I know NOTHING of transmissions, so excuse the stupid wording and whatnot, heh)

2nd is the real pain. It simply won't tolerate downshifting. Well, not even downshifting, I have to really hold the stick hard in the 2nd position until I've given it a little bit of acceleration or it will drop out of 2nd. With the tiniest amount of acceleration it will grab second and hold it just fine, but with no acceleration or deceleration it will just drop it.

I have some people telling me it needs a full re-build and others telling me it's just a bad syncro. What do you guys think?

EDIT: btw, it's got a brand-new slave cylinder.

 

Could be more than just one problem. It could be something bent in the shift rails, or bent shift forks. The down shifting problems are probably due to bad blocker rings (syncros). I've had 2 of the T5 transmissions that wouldn't down shift into a gear and when I replaced the blocker rings they worked fine. These were the non world class transmissions with the brass rings. It is very common for the later world class t5 rings to break off the ears and not work at all.