[Kputz]

Most Ford 9" rears are lubed with 80/90..whatever..and then the "additive". Most cars equipped with a 9" for racing purposes (and they are legendary) don't run with the additive. Aside from the considerable noise generated running sans additive the difference seems to be that they hook up better, the running life of the rear end doesn't seem to be the issue. I know guys that change out trannies in A Sedans twice a year that haven't touched the rear in years.
The question begs itself....what does the additive really do? It obviously supplements the lube for a purpose, but is this purpouse to thicken the lube to prevent the noise?? Any FoMoCo wizards out there know the skinny?