I have heard alot of good things about Redlines products, especially their MT-90 gear oil. I know alot of people who run it in their tranny and transfer case and say it makes a big difference in smoother shifting after cold starts and in the summer heat. I'm gonna be doing my clutch in the next two weeks and plan on refilling the tranny and transfr with MT-90. As for running it in the diffs I imagine it would be just as good as any other GL-5 type gear oil. I beleive Summit racing has good prices on the Redline lubricants.