People like you - who have no clue how a 4x4 operates - should not own one.
First - you should only switch into 4x4 when on dirt roads, snow, ice, or wet raining roads.
Second - all four tires should be identical - same make, same model, and same number of miles.
When you engage 4x4 two things happen. First, power is taken from the transmission and transferred to the 'transfer case'. That power is sent to the front driveshaft with distributes it to the left and right front wheels from the front differential. Each front tire will have a locking hub - some are automatic and manual back up, some are just manual.
That stuttering and difficulty/resistance when making turns? That is your front hubs being very, very unhappy because you are on solid pavement and/or you front tires are not matching. You are literally tearing up your 4x4 front end.
When you exit 4x4 your vehicle should near instantly disengage those front hubs. Running it with those engaged is going to cost you thousands of fix, and since this is a 2003 - it will cost you the vehicle.
When you exit 4x4 you need to make those hubs disengage. If they wont come out on their own - then stop the vehicle and manually unlock the front hubs. You will find a movable sleeve at the center of your front tires, turn it. Sometimes you just need come out of 4x4 and just put the thing in reverse and you will hear the hubs drop out. Others you need to put the vehicle in neutral, then come out of 4x4 for the hubs to drop out.
The reason having identical tires are important - in 4x4 all the tires are locked together by gears - if three tires are Brand A and one tire is Brand X the Brand X is going to be a tiny big bigger or smaller. Bigger - it will bind up it's gear - all of the tires loose torque (power) - and the bound gear is prone to failure. Smaller, the other three will be forced to bind, torque will be lost (lost power) and all the gears along the drive train will get excessive wear and tear.
That you think this is transfer case fluid related - is scary. That like someone giving your chicken noodle soup for a broken leg.