Managed to grab a couple of hours to do some long overdue spannering on the truck today and one of the jobs I like to do following each off road excursion is to check the gear oils for contamination. This time I have water contamination in both my rear axle and the transfer box, last time it was just the transfer box the couple of times before I had no contamination. I'm not so bothered about the contamination as it comes with the territory I guess, maybe I should consider extended breathers at some point. What does get me though is my front and rear axles spec 80w-90 gear oil and the gearbox and transfer box spec 75w-90 gear oil. It would be great to be able to just drop one oil into the lot, so can I put 75w-90 gear oil in my front and rear axles in place of the 80w-90 or not? What is the difference between these oils? My main reason for asking is that I can buy pretty much 15L of 75w-90 gear oil for £50 and would then only ever have to carry one oil for emergency use and or keep in stock one oil and only ever need to buy one oil at a better price due to the quantity I'm buying at any one time.
