Mine has been like that for a long time. In fact, now 4th gear is beginning to grind when I shift fast into those gears.
There's discussion of a friction reducing mixture being installed or a "tranny cocktail"
This discusses it It might help a little, but I doubt it.
I've just adjusted to shifting into third by momentarily holding the clutch pedal down just a little longer before I put it into 3rd (or 4th), but I admit, on fast runs I shift normally and I always get the grind. But for normal driving I just hold the clutch a small bit before shifting and that allows the tranny and engine to "line up" and I don't get the grind.
But T. is right, a rebuild is the only solution to the problem. Depends on what you consider worth it.
Good luck
