not very far
You can have worn universal joints, wear or low oil in transfer case or differential(s),transmission low on fluid or needs band adjustment. Seems to be one of these problems along drive train.
As long as there are no leaks and it never gets low of lubricant modern differentials should last the life of the vehicle. For even more insurance against failure have the lubricant changed at 100,000 miles and install synthetic lube.
low on fluid
After the Jeep is warmed up, if the creaking noise is noticable during turns at low speeds, then its probably the rear differential. Go to the dealer and have it serviced. All they do is replace the fluid and seal but they use a special lubricant additive.
your accuater is starting to go its located on the front differential drive safe
Yes, if you want to destroy your engine.
Reverse, Drive, Low gears
I would say, Low, Second and Drive.
Manual or Automatic?? In either case, most likely the linkage. Manual, might be the syncronizer gear or low on lubricant.
Several possibilities: If you have an All Wheel Drive (AWD) model, it could be that the differential fluid is low or the differential gears or bearings are failing or one or both of the wheel bearings are failing. If you own a two wheel drive (2WD) model (which do not have a differential) it would possibly mean that the wheel bearings are failing.
If by "rear gear" you mean the differential, that joins the driveshaft to the rear axle: If run without sufficient oil it will overheat and eventually be ruined. Ordinarily the rear differential oil seldom needs changing, as unlike engine oil it does not have combustion byproducts constantly contaminating it. If however you drive through floodwaters, water can enter through the vent, which will ruin the differential oil. If you run through flooded water you should have the differential oil changed.
When driving in fog it is best to drive with low your light on low beam. This will ensure that you get clear vision. You can use fog lights if you have them on your car and do not speed.