I saw this post and thought I would chime in a little.
As for the difficulty shifting the transfer case. The gears and splines inside the T-Case are designed to slide across each other. However, if they have enough pressure on them they will resist. The resistance can be formidable. Don’t force it!!
The pressure can be because the front tires are turned, or perhaps tire pressure is varied so the effective gear ratio front to back is creating a bind. Or perhaps you just have your foot on the brake so the pressure cannot be relieved. Move the vehicle a little, let it roll, take your foot off the brake so it can move, turn off the engine for a second, or shift between a gear, etc. Any of these will unload the pressure.
When engaging the T-case. Keep in mind that there are splines and geared parts that have to fit together. It is not at all uncommon for them to be misaligned at the moment you are about to try and engage them, as you do when you go from 2WD to 4WD or 4WD-hi to 4WD-lo. Never force them! Hulk Hogan and the linkage don’t have enough strength to over come 2-pieces of hardened steel butted against one another.
The teeth have ramps, so that perfect alignment is unnecessary. But sometimes they just need a little help from you. You need to do something to make the gears and splines change position so they are closer to lining up. Same drill. Move the vehicle a little, let it roll, take your foot off the brake, turn off the engine, or shift between a gear, etc. Anything that allows the gears to move just a little, so they can align.
Periodic use of the gearboxes to avoid problems does have some basis in fact. It all gets down to cycling fluids, and generating enough heat to expel any moisture inside the gearbox. A gearbox can be a T-case, rear end, or transmission.
Condensation and moisture are what you should be most concerned about. Gearboxes are made from metal. They live outdoors. They get cold. They get hot. Gearboxes are vented to the atmosphere and breath. Even slight changes in temperature cause this breathing effect. Drive down the road and you create heat that makes the gearbox exhale. Stop at a light, cooling commences within 20 seconds and the gearbox starts to inhale. Got it?
Highway speeds can take a new rear end up to 250F degrees. Park it in the driveway for a few days, and you get a BIG inhale.
Moisture is in the air everywhere, especially in humid climates. Deserts too, but not nearly as much. Moisture forms droplets on cold metal parts. These droplets settle in the oil, and on the exposed metals part inside the gearbox. If the parts have been sitting for a long time (months) they will probably have very little oil coating to prevent rust from forming. If the vehicle sits long enough, the breathing continues day and night while the car sits. The droplets can turn into puddles or mix with the oil. Oil will turn grey, white or brown, as it gets contaminated.
Hope that helps.
Just driving normally once a week for 25 miles should be enough to expel moisture. If your car sits for long periods, just take it out for a drive. By the way the breathing cycle also happens inside the engine.
