To make a noise, something has to be moving. To make a constant click or whine, something has to be turning. Well, thinking of all the turning parts in the drive line, it could be a few things.
So you have the engine turning the transmission, which turns the T-case, that is turning the drive shafts, which turns the pinion gears. The pinion gear turns the ring gear, which turns the spider gears. Now depending on which carrier you have in the rear axle (LSD or Open), force is applied to the axle shafts according to resistance. Front axle wheel side bearings are sealed HUB unit bearings and are non serviceable. Diff side bearings are replaceable, but are inside the diff tubes and carrier. Brake rotors, and discs spin inside a caliper and next to a dust shield/brackets.
Rear LSD clutches will not accurate until slippage of one wheel happens. With an Open carrier, power is given to the wheel with less resistance. Front carrier is open on all Explorer in stock configuration.
Front CV's are directly fixed (splined ends) to the wheel hubs, so they spin with the wheels. The Joints inside the boots on these have large ball bearings, that spin as well.
Drive shafts have U-joints, that spin with the shaft, but at different rate of speed. The front drive shaft has 3 joints and 1 center bearing. Depending on your model, it can have all U-joints or a CV joint to the T-case. Rears have 2 sets of U-joints.
Ok, so that about covers the basics of all the turning parts as a whole.
Clicking can be caused by a worn / stressed part that has lost it's tolerance or a part that has lost it's mechanical connection, and has moved out of place, and is now touching something it is not meant to as it moves.
Whining can be caused by a moving part that is making a constant connection against fixed surface.
CV's make a clicking noise when the ball bearings are no longer held to tolerance and get hung up, stuck, and snap in/out of socket as they are forced to move in the machined bearing basket. When the wheels go up and down the CV lengthens and shortens with the travel motion. The CV is made to move in/out to accommodate the motion. This mechanism also fails as it wears. If a CV boot cracks, rips, or simple becomes unsealed, the joint can become contaminated with moisture/dirt, and break down the factory lubricant, causing bearing failure over time. These make the most clicking noise when turning as the stress is placed more onto one side of the bearings then the other.
Differentials. I'm going by a 2nd gen front D35 and the 8.8 rear. Both have axle bearings on each side. Front are on the diff, and rears are on the ends of the housing tubes.
Front diff is a simple open carrier that has bearings inside. These bearings could burn up if the fluids are bad, or low, as a lot of heat is generated from the gears meshing. When the bearings break, they will let you know as it can be violent. When they burn up, they can whine / squeal. Early 2nd gens 95-96 have CAD axles, which allow the front to stay free spinning at all times until activated. 97+ have a live axle, which has some static power going to both wheels at all times. These axles have more stress / wear then their earlier versions.
Rear 8.8 is the same as the front with bearings, but the LSD versions have clutch plates that can break and fall into the gears and get chewed up, or jammed into the carrier.
U-Joints. When these go bad, they can cause either a thunk, or a vibration. The thunk is when placed into gear because of the slack, and the vibrations are at speed. The front center bearing or front CV can make a click or whine if going bad.
T-case. The stock 2nd gen cases have electric clutches, and sensors that rely on proper info given from the vehicles computer and sensors. and as such, have a ton of parts that can fail, and they do often. This case (to me) is the weakest link in the entire drive train. Clicking, whining, and thunks, can all be made with this part, so it is high on the list of being suspect for the noises heard. Plenty of info here on this part in this forum.
Transmission. Many different models in the 2nd gen, each with their own issues. This falls into the same suspect list as the T-case for noises. Autos are all run under hydro pressure, and manuals are all mechanical operated. Auto trans make noises that are more associated with fluid pressures and can vary greatly in sound. Manuals trans (and T-case) are less prone to failure. Manual trans have parts that do wear, and can make obvious whining noises, but are more of a mechanical metal to metal type of noise.
So what does this all mean when you hear a certain noise while moving, or turning?
Hopefully, this helps you pinpoint where the noise is coming from, and as such, can make a determination of the cause. From here, you can take an appropriate action and make a decision if it is something you can repair yourself, or take to a professional to repair. CV's and U-joints are simple DYI repairs. The rest is more challenging, and might require a mechanic to repair, depending on your knowledge and skill sets.
Because you said clicking and while turning, My Guess, is the CV's, but.. it is best to look at everything in the drive train to make sure, before replacing parts. Sometimes a brake caliper bolt can come loose, and fall out, causing the caliper to do this as well, so check them to make sure they are right. You will notice this in reverse if it happens, as it forces the caliper towards the wheel center as the wheel moves if it is a lower bolt.
Happy hunting!
