My 1998 ford explorer makes a loud noise (like an plane landing,when i take my foot of the accelerator, when i try to turn left or right it makes a loud grinding noise and won't move forward, it has only recently started to do this, it doesn't do it all the time maybe once or twice a day. When i stop the vehicle and change into neutral & select the 4 wheel drive selector by putting it into high or low 4x4 i hear a bang noise, then when i try to drive it is O K but then when i try to stop the noise and the problem comes back again, then other times the problem goes away and the vehicle is fine to drive again, the problem started two weeks ago and does not occur every day.

auto locking just makes loud noise , Where ? Inside a door ? Bad door lock actuator .

Check the front suspension ball joints and steering joints. Check wheel bearings and adjustment. Check shock absorber mounts for condition . Check steering insert condition and top mount rubbers and bearings if McPherson strut set up.. If you have a steering shock absorber then check it's condition and mounting

axle bearing is bad

Whining noise is probably in one of the pulleys or belts. Probably the power steering. And the popping is probably CV axles.

could be a rod bearing going bad.or could be bad gas causing it to spark knock realy bad. try to put some 93 octane in and see if it goes away.

this is a tough question to solve w/out more info. But, when you let off accelerator does it stop? if yes,get the universal joints inspected. No? then i would have the front wheel bearing hubs checked,and if it is neither of those issues i would have the rear axle inspected for a bad bearing,pinion mesh.

I can almost guarantee you it's not serious. Just u-joints.

FORD: 1997-2000 EXPLORER, MOUNTAINEER
ISSUE: A "knocking" noise at start up for up to 2 minutes from the left hand front chain cassette area may occur on some vehicles. After engine shutdown, the tensioner oil supply gallery empties. The noise may be due to air entering the left hand tensioner when the engine is restarted.
ACTION: Replace the left hand camshaft tensioner with a revised Tensioner Kit. Refer to the Instruction Sheet within the Tensioner Kit for service procedure details.
WARNING: THE XU2Z-6K254-AA TENSIONER KIT IS FOR INSTALLATION ON THE LEFT SIDE OF THE ENGINE ONLY. INSTALLATION OF THIS KIT ON THE RIGHT SIDE OF THE ENGINE MAY RESULT IN ENGINE FAILURE. IF A TENSIONER IS NEEDED FOR THE RIGHT SIDE OF THE ENGINE, USE KIT XU3Z-6K254-BA.
PART NUMBER PART NAME XU2Z-6K254-AA Tensioner Kit - Left Side XU3Z-6K254-BA Tensioner Kit - Right Side

SECTION 303-01B: Engine — 4.0L SOHC 1998 Explorer/Mountaineer Workshop Manual
IN-VEHICLE REPAIR Timing Drive Components —LH Hydraulic Chain Tensioner Removal and Installation

1. Remove the upper intake manifold. For additional information, refer to Intake Manifold—Upper in this section.

Intake Manifold —Upper Removal

1. Disconnect the battery ground cable (14301). For additional information, refer to Section 414-01 .

1. Remove the air cleaner outlet tube (9B659); refer to Section 303-12 .

1. Remove the bolts and the accelerator control splash shield.

1. Remove the accelerator cable (9A758) and speed control actuator cable (9A825).
   1. Pull up on speed control actuator cable to remove.
   1. Rotate the throttle body cam and remove the accelerator cable from the cam.

1. Remove the screws, the accelerator cable and speed control actuator cable.

1. Disconnect the RH upper intake manifold vacuum connection.

1. Disconnect the idle air control (IAC) valve electrical connector.

1. Disconnect the TP sensor electrical connector.

1. Disconnect the engine vacuum regulator (EVR) and the variable induction system (VIS) solenoid electrical connections.

1. Disconnect the crankcase ventilation hose (6853).

1. Disconnect the power brake booster vacuum line.

1. Remove the 12 bolts.

1. NOTE: Inspect the O-rings and replace as necessary.
   Disconnect the LH fuel vapor management valve (VMV) hose.

1. NOTE: Inspect the O-rings and replace as necessary.
   Disconnect the RH VMV hose and remove the upper intake manifold.

1. Remove the thermostat housing. For additional information, refer to Section 303-03 .

1. Remove the LH camshaft tensioner.
   • If using a new washer, tighten to 44 Nm (32 lb-ft).
   • If using the old washer, tighten to 67 Nm (49 lb-ft).

1. Remove the pipe plug, and the oil volume reduction plug.

1. NOTE: Be sure to install the new oil volume reduction plug supplied with the hydraulic chain tensioner.
   To install, reverse the removal procedure.

please rate as fixed if this helps you

Replace the IAC valve.

Please check for your transfer box.