[Fot] Does anyone know of an additive that improves a TR6 tranny's smoothness of operation?

[William G Rosenbach]

The folks at 3R Racing, in cars they prep for vintage racing will use
Redline MT-90 (GL-4) in gearboxes that are about to be due for rebuild. I
used it in a Renault transaxle and it greatly improved shifting, both up
and down. With mineral base, multi vis GL-5, the hotter it got, the worse
the shifting got very quickly. Redline was not as much effected by temp.
The synthetic did not like to stay in the gearbox, however. 
Changing to a straight weight, GL-4 mineral base oil was a huge
improvement over the GL-5, almost as good as the Redline, though not
quite as good hot, and it stayed in the box. 
I conclude the most important thing was a GL-4 oil.
Bill