I have to disagree that Pennsoil synchromesh is the 'wrong stuff'.
The really wrong gear oil is one that says GL-4 OR GL-5. There is no either or. It's one or the other, so if it says it's both, it's marketing BALONEY. To know the truth about the GL ratings, its a DIFFERENTIAL rating, not a gear box rating. It has to do with the amount of sulfur/ phosphorus in the oil. The GL-5 has a higher content S/P and steel syncros can handle that rating. But the brass synchros in the 'classic' boxes, like the 02A, 02J and 02Q, the GL-5 makes a sacrificial black coating that attaches so hard, that when it does it's job, molecules of the brass will be torn off with the coating. After not many miles, you look at your gear oil and it shines like panned gold.
To just say, 'Use Redline'. There are PLENTY of Redline oils that are 'the wrong stuff', like say for example, 75-90 GL-5. Although the MT-90 should be right, we have had problems with a tranny using it. Personally, if I am going to spend twice the price on gear oil, but my feeling is the Redline Light Weight Shockproof is probably the best. But at $20 qt, it's expensive.
The conventional gear oil that we have used without issue is Pennsoil Synchromesh.
If the oil doesn't improve the shift, you are probably into some synchro, bearing and possibly gear replacements.