Noise when engaging 4wd

Sounds like a bad 4WD actuator. Very common failure, but pricey part.

There are actuators on the front axle and the transfer case, check them both.

This would your transfer cause mod under dash or your t/case motor is bad

Possible actuator motor issue have it tested.

Sounds like your axle seals have leaked out all the fluid. Take it to a garage and get a free estimate on it and they will check your axle seals.

chec fluid in transfer case and also the front differential--git a haynes book at a parts place for procedure

The clunking noise could be coming from three different areas. Either the front or rear differentials could make that noise along with the transfer case. I would initially be looking at the transfer case as the culprit since you mentioned the 4wd light coming and going. My thinking is that the 4wd engagement solenoid is malfunctioning and trying to bring in the 4wd, then releasing it. The only good way to check the function and noise for this is to put the car on a lift.

if you are driving on hard surface ( sealed roads) in 4wd then don't as if damages the drive train
what is happening is that there is a torque wind up from the front and rear wheels running at different distances and the cluck you hear is when at some point that torque is released and allows the selection to disengage or engage
4wd is for use in slipper conditions unless you have an AWD which will become 4WD when required by you after selection of the control

Sounds like the front drive axles are worn.My 89 MPV had the same "clicling" noise with an occasional clunk.The reason you feel it more in 4wd mode is because power is now being transfered thru the worn axles. I replaced both sides for approx $375(Axles rebuilt were 130 for drivers side and 110 for passenger side the rest was labor)

1. I would suggest that you engage your 4WD while you are in full stop and/or safe range of 5mph, however as claimed by the local dealers your vehicle is capable of engaging even while driving. Engage your 4WD while moving only when necessity requires.
2. That clicking noise while turning extreme right or left would be the birfield of your axle and would only mean your front hub is still engage even though you have disengaged transfer case.
Have your front hubs cleaned of old lubricants or grease due to non usage. dont use grease as lubricants, use thick oil such as gear oil or silicone oil. and use your 4WD every now and then.

Do this first then check if you still feel somtehing is loose on your suspension and others.