Royal purple sucks in the tranny tried that, but I used it in my t-case & rear diff no probs. MT90/MTL was the best that I've tried for a early 1Gen tranny, but I'm sure there is other options, but I usually avoid an oil that says it is ment for both GL-5 & GL-4 and aim for GL-4 specific oil, except Motomaster full synthetic - that didn't work well either for me in the tranny perfect for t-cases & rear diffs though.