If you haven't been off-roading with it, and the free/engaged selector is turning freely, then I wouldn't mess with it,
but if the hubs have been removed recently for any front-end service, been off-roading, etc. & you are looking to do some preventative maintenance, then I'd just pull the manual hubs, clean up the spline, inspect the inner hub, add a tablespoon's worth of grease to each hub, and reinstall.
re: which grease: a good #2 weight moly-based grease will work well, like this:
* Unless there is obvious dirt/grime in the hub assembly, I'd just clean up the excess grease & add some fresh grease to it.. The hubs come lightly greased from the factory w/ an extra dab of grease in the top cup, fyi.
I put the Sporty in 4x4 mode every 4-6 weeks to make sure everything gets lubricated / is working ok, either in the yard with the utility trailer attached, or on a dirt road nearby..
I'd engage spin the manual hubs every so often (even if you do not go full 4x4) to keep the grease moving in the hub, even if it's a short distance - not being engaged for a season (3-6 months) is probably ok, but if longer I'd pull, inspect, and re-grease, only because grease has a tendency to harden/degrade with non-use.
Thank you for the info, and especially on which grease to use. This is my first 4x4. Dad had a couple 4x4s over the years while I was growing up but was too young to help much with mainteneance. By the time I was old enough to help, no more 4x4s, just cars.
The driver's side hub was getting a little hard to move so I decided to clean and regrease the hubs. Glad I did because I found the driver's side hub had about twice as much grease as it should have and it was old. The passenger's side barely had any grease at all. Kinda looked as if someone cleaned out both hubs but then put all the grease on the one side. Now they both move smooth as butter.
Thought of a couple more questions:
1) While I had the hubs off I noticed that the splines have a hole in the center. Is the hole for the stock vacuum hubs, or is it a grease fitting of some sort?
2) For post mudding maintenance, how would you clean out the hubs? Just wipe them out as best you can, or can you use some sort of cleaner?
Nice catch on the hubs - some regular preventative maintenance is all they need to last you many years..
re 1) - that hole is for the stock vacuum hubs, just leave it as-is,
re 2) - some soapy water and a clean cloth to dry is all you need.. (I wouldn't use a pressure washer too close to the hub selector, to avoid pushing water past the seal..) -- A plant sprayer bottle or empty glass-cleaner bottle filled w/ soapy water & a nylon soft-bristled wheel brush works well for getting any dirt/grime out of the manual hub cap here..