What makes the brass synchro rings of today any different then the rings in past transmissions, for example the transmissions built before synthetics oil like Castrol Syntorq was available???
I have had many standard transmission in many different cars. They have come from the factory with everything from 90W to Automatic Transmission Fluid(What genius thought that one up

) to whatever castrol syntorq is.
I am in the process of rebuilding my NV4500 at 92k because of a bearing failure. Actually all the bearings look pretty bad. I can only assume that since I know the history of the truck, no more then 6k lbs about 30% of it's life, that the gear fluid from the factory, must not be adequate. In response to a lack of lubrication, the oil turned and awful shade of brown, thickened, and my bearings went out.
WHAT MAKES THIS TRANSMISSION SO SPECIAL THAT IT REQUIRES $25/ QUART LUBE TO MAKE IT RUN??? On the inside, it looks just like my NP465 that I have in my jeep with an extra gear. Both have brass synchros, and both look about the same size and strength. Why can I put five dollars of Costal 75W 90 in that transmission for 90k miles and not have a problem, but my $25 per quart transmission will not even make it to 100k???
On the back of the $25 bottle of snake oil it says "This unique synthetic transmission fluid is formulated for the NV-4500 5-speed wide ratio transmission. Maintains proper shift quality in cold temperatures. Do not use in other manual transmission unless specified" I live in Houston, it never gets cold here. What do I care about cold temperature shift quality. I need the one that says it maintains shift quality and bearing longevity at high temps. I can also only guess that it is not good enough for other transmissions thus that disclaimer.
I hope that some "oil engineer" or someone who really knows transmissions can chime in here and tell me why I have to use syntorq other then saying, "that is what it calls for for warranty issues(note my milage). I have heard about the brass synchros, but I can ussure you the brass synchros in my other manual transmissions are just fine with the cheap stuff.
In my transmission, this oil was not good enough and I am looking for something better.