4th gear vibration

[olddog]

I have a TKO 600 that only had about 3K miles on it when I bought the car. It has alway had a vibration in the shifter. I replaced a bad U-joint and had drive shaft ballanced right after a got it. That got rid of most of the vibration, but not all. I had kind of assumed that the short drive shaft and angles were causing the vibration.

Anyway I got to paying attention to this. If I lightly push the shifter, as if to pull it out of gear, I can feel the vibration real bad. However the vibration is only there when pulling. If I decellerate, it is smooth as silk. Ok that makes sense as the gears are meshing on the other side of the teeth, so I must have a chip on one side of a tooth.

I can do this in any other gear and the tranny is smooth as glass. Now for the kicker. I have noticed that sometimes it is worse than others. Tonight I shifted into 4th and it was smooth as glass, no matter what the speed or power level. After testing this from 1500 rpm to 3500 rpm and flat to the floor the darn thing was perfect. So I pulled it out of 4th and stuck it back in and the vibration was back. I tried it several times and the vibration changes from better to worse. So it appears that it depends on which tooth happens to match up as to how bad the vibration is and that there actually is a set of teeth that are perfectly mated and run well together with no vibration. I'm guessing that these teeth were running together when what ever damage happened to occure.

Also the trany has the .63 ratio 5th gear, which I do not like.

So if I pull this appart, what is the likely hood that I can stone out what ever ding is causing the vibration or will the gear need replaced?

Assuming I do all the labor my self and only purchase parts:

What would it likely cost to replace 4th gear like for like?

What would it likely cost to replace 5th gear with the .82 ratio?