Reply to "Grinds in 2nd and 3rd"

Sychros are around $300 each for this trannie. The gasket kit is $300. Gears are $900 each.
If there is wear, hopefully it is the sychro and not the gear.
What happens is that when you push on the gear lever, it pushes the synchro against the gear and it works like a break to slow down the spinning gear. When the two are coordinated or synchronized the slider is able to lock the gear to the mainshaft.
Reverse or second gear in almost all manual transmissions are what have the most grinding problems. Reverse has no synchro. One can normally use second gear to slow the spinning down, by shifting into second first, to engauge reverse without grinding.
2nd is the largest gear on the cluster and has the most mass.
That makes it the most difficult to slow down.
The synchro is supposed to be the fuseable link, meaning the cheap replacement part.
The gear hat already is very polished from the machining process to begin with.
The synchro is the female component corresponding to the hat on the gear. When it becomes polished then you loose the breaking effect of the synchro. Kinda like glazed brakes. They very rarely completly fail. They are geneally a fancy manganese-bronze alloy.
Since synchros work on a frictional basis,
and sometimes when synthetic lube is used it is too slick. It doesn't permit the necessary friction for the synchro to work properly.
Sometimes by simply returning to the original petrolium gear lube, the problem is solved. Sometimes.
What lube works best is a function of the synchro design itself.
The BW T10 synchros which are also used in the Doug Nash and the Richmond, Supper T10's are like this. They don't work as well as they should with synthetic gear lube. The real problem is that they are too small for the size of the gear they are supposed to slow down. They are used because of the price. They are less then $10 each.