I am buying a GTUs rear diff off of another forum member (very nice fellow). Well I wanted to know if I needed an additive, since I do not know hardly anything about differentials (learned alot in the past few days). So I emailed mazdatrix and they said the Neo brand synthetic gear oil does not require an additive and that I wouldn't need it anyways since the diff is a viscous type. Is this info correct? I have just been confusing myself with all these different types of differentials and what type of gears or clutches they use, which ones need an additive, which ones came in what models, and in what years. Somebody throw me a bone here!

 

true. viscous diffs use a fluid internally that when sheared at a high enough force (2 very close plates rotating at different speeds) changes viscousity (thickens) and transfers power. imagine trying to spin a plate on a metal table with a light oil in between, now think of it with a heavy racing oil. however it is a sealed unit that you will never have to change the fluid in. clutch types need the aditive in order to maintain friction between the rubbing clutch packs to transfer power.

 

Thanks! So the differential out of a GTUs with the 4.30:1 gear ratio does not require any addititve?

 

no