Tell yuou what, if it makes you feel any better. I tore down two Polaris transmissions and repaired them and they are nothing but big gearboxs. Very un complicated. Big gears with a silent three link chain, pretty much. I am convinced any slippery substance would be fine. I have put the Polaris AGL in there, ATF(Dodge +3) because it is referred for transfer cases, which a Polaris transmission resembles), and Motor oil 5w20 and 30 wt, with no difference in performance or noise. By exmination, I would suggest a thin oil(definetely not a gear oil) simply because there is a magnet on the bottom and it would be better if the metal shavings do not become suspended, but rather drop to the bottom of the case to the magnet, and these transmissions produce alot of shavings, its natural. I have found the transmission magnet covered in a 1/2" of shavings in a brand new quad. Its just the nature of the beast. these are robust transmisions and very simple in design. really you can go on Youtube and see the insides, not much there, I speak from experience and not from "reading about it" or what the "manual says". What I can tell you is in 1991 before Polaris had there own line of lubes, they reccomended 30wt oil and these transmisions have not changed since, except in appearence on the outside.