I have a 2018 XLT 4x4, bought used in Alabama around 35k miles, recently moved to Alaska and now have 76k. The front end has a humming or groaning sound when I switch to 4h. There’s no rattle or grinding either, just the hum. That sound doesn’t change when I’m turning either which way, and it has gotten noticeably louder since I started really using my 4wd this last winter. I’m worried that since it probably wasn’t used liberally in the south that moisture would have gotten in and ruined the bearings or even worse the gears. I’m going to change my front diff fluid this weekend, but are there any other things I can check while I’m already working on my truck?

 

You have a lot more machinery turning in the front of the vehicle when in 4X4. Some more noise is expected. You don't have to use 4X4 a lot for preventative maintenance. Just a few miles every month or 2 in order to keep everything lubricated. If there is any damage it is more likely due to overuse now on roads where it isn't needed.

Unless traction is really bad you'll do more damage operating in 4X4. I've owned a 4X4 since the 1970's and while I don't see a ton of it here in GA, I've driven all over the Rocky Mountains in snow during winter. 4X4 is best used only as needed to get you moving or through rough patches. It isn't the same as All Wheel Drive which is fine to use all the time and on any road surface.

Virtually all damage that I've seen to a 4X4 system is due to operator error. People either never use it and then it doesn't work when needed, or they use it on surfaces where traction is good and they break something.