Redline is great product. We use MT-90 in the transmissions and Tcases here at Marlin. Redline also makes this super cool product called shockproof, which is a multi viscosity. Shockproof is cool for the diffs, but I think its a little too sticky and gums up transmissions and tcases. Mobil one I know makes some good products too, but im just not familiar with them, and haven't ran them personally.
