Sorry to tell you this Crkid but Mobil-1 75-90 fully synthetic gear lube is actually not good stuff for your AX-15.
Per the information at Mobil 1 Synthetic Gear Lubricant LS 75W-90
you will find that Mobil-1 75W-90 uses sulphur-based additives to achieve its GL-5 rating. Sulphur-based GL-5 additives are bad/harmful to the "yellow metal" (brass) synchronizers in your transmission. No worries, it will not cause immediate damage but I would change it to a different gear lube such as Redline MT-90 which is a GL-4 75W-90 or a synthetic 10W-30 motor oil. The sulphur-derived additives used to give it its GL-5 rating will cause long-term accelerated wear on the synchronizers but it doen't happen immediately.
Old Mopar user guides incorrectly said to use 75W-90 GL-5 but that was later quietly corrected to recommend a 75W-90 GL-4 gear lube which does not have the sulphur-based additives.
There are SOME 75W-90 GL-5 gear lubes like from Royal Purple and Amsoil that are safe for yellow metals but they have to specifically say that which those two brands do.
No worries on the recommended synthetic synthetic 10W-30 motor oil recommendation seeming to be the wrong viscosity. 10W-30 motor oil and 75W-90 gear lube are essentially the same viscosity, gear lubes and motor oils are measured on two different viscosity scales.
On why I prefer a non-sythetic in my axles, tests from companies like Currie showed in extreme uses that the ring & pinion gears run cooler when filled with a conventional gear lube. For most of us, it's a non-issue.