I never understood oil changes based off time. What if you only drove your rig 10,000 miles in 2 years. Would you change it or wait until a normal suggested mileage interval which is 30,000 miles. I always base oil changes on mileage only.
I know it's suggested to drive some in 4wd every month but how many actually do this? Both my rigs were driven by people who did not go 4wheeling because it was clear by the condition of the vehicles and from the people I bought them from. One was a total grocery getter that a woman drove and the other was driven by a 70 yr old woman who sold it because she bought a Prius. Both rigs shift in and out of 4wd without issue and the transfer cases are fine - no weird noises or grinding. So, while I think it's probably smart to exercise the 4wd system from time to time, I don't buy into the need to drive it 5 miles in 4wd every month. I go months every year without shifting into 4wd in both my rigs and I haven't had any issues. Now, would you want to go years, probably not, but I know without a doubt both my rigs probably went for years without being put into 4wd and they're fine. My 98 has a locker and even that engaged with a little persuasion of driving a weaving pattern for a bit and I bet that thing might have never been engaged by the previous owner.
OP, take up the challenge of turning wrenches if you have the space to do it. It's not hard.
This video will help you out.
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