4x4 not working (91-94) The purpose of this thread is to consolidate troubleshooting information in one area so people can find the correct information quickly. It is not intended to become a huge run on thread where people ask questions as this would defeat it's purpose. Questions should be asked in other threads and any additional information deemed appropriate will be added to this one. Interactive How Cars work Animation. Click on Drivetrain and you can see the various steps to go from 2WD to 4WD (Note step 5 is incorrect for Ford Automatic hubs, To unlock Ford Autohubs you must reverse direction for several feet). 4x4 High The 4x4 system can be shifted on the fly into 4x4 high at anytime. If pressing 4x4 fails to activate 4x4 (The dash and button 4x4 lights are off) then you have a failure in the system (Dash button, 4x4 module, Shift motor). If you listen carefully you should be able to hear the relays in the 4x4 module when you press the 4x4 button. If you cannot hear the relays recruit a friend to sit near the module and listen. If the relays make noise it indicates the 4x4 module has received input from the dash button and the problem lies in either the 4x4 computer or the shift motor. If you cannot hear the 4x4 relays then you will need to verify the 4x4 module is working. The most common problem is a broken Stop Bumper within the Shift Motor. The worm drive on the electric shift motor puts out a LOT of Torq. As such when returning to the 2H position the shift motor doesn't stop on a dime and needs the Stop Bushing to Prevent: The Geared Position Sensor from traveling outside of it's operational range. When this occurs the 4x4 module becomes lost, and will no longer shift the T-Case as it cannot determine the position of the T-case selector shaft. The Geared Position Sensor from getting JAMMED against the metal stop. Once it gets jammed against the 2H Metal stop the shift motor may not have the power to Un-Jam itself when you push 4x4. See the Shift Motor rebuild thread on how to fix the Shift Motor. To re-sync the shift motor: Mark the Geared Sensor cover to case Remove the Shift Motor from the T-Case Remove the Geared Sensor Cover Remove the Geared Sensor Turn the T-case selector shaft to 4H Re-install the Shift Motor case (no bolts) Re-install the geared sensor Turn the shift motor case so it's bolts holes align with the T-Case (install bolts) Ensure Geared Sensor is seated into housing (never force with cover) Re-install the Geared Sensor cover When you turn the truck on the 4x4 system will see the position somewhere in between 2H and 4H. When you press 4x4 it will move to the correct position. Notes: If the Selector shaft was in 2H (default position) it could get jammed against the stop making it difficult to align and install the Shift motor mounting bolts. Placing the Selector shaft in between 2H and 4H gives you a 1/2"+ of play forward or back when installing the case allowing you to easily align and install the shift motor bolts. If the Geared Sensor isn't seated all the way you can gently tap it in with a rubber/plastic mallet. Never try forcing it down with the cover as you'll damage its electrical contacts. Checking the 4x4 module (rear trunk). Unplug the two connectors that plug directly into the module (left side), turn the key on and push the reset/test button on the module. The LED should flash four or five times and stop. If the LED flashed the four or five times, the module believes it is ok internally, and you'll need to check the external parts like the 4X4 switch, shift motor, magnetic clutch and wiring harness. If the LED did not flash at all or kept flashing continually, the module is telling you that it is damaged internally. (check for power & ground). Click a thumbnail for full size image Its fairly common on 1st Gen explorers to periodically have a dimly lit LEDs next to the 4x4 buttons. Mine tend to appear dimly lit a few times per month, more often when it gets cold out. Rest assured you vehicle is not in 4x4 unless both the dash and button lights come on. 4x4 High To engage or disengage 4x4 High: Press the 4x4 button (anytime, nothing else required!) 4x4 Low To engage or disengage 4x4 Low you must: 1st be in 4x4 high Transmission in Neutral Clutch depressed (manual transmission) Foot on Brake (mph<3) Now Press 4x4 Low HUBS Hubs (automatic & manual) are used to lock the front wheels to the axles allowing the wheels to be powered. Locking is a purely mechanical action and is insensitive to the electronic 4x4 system. For manual hubs the locking occurs when the hubs are turned to the "Lock" position. For automatic HUBs the locking occurs when the axle shaft begins rotating within the HUB, which causes the splined engagement mechanism to idle up on the engagement cam which locks the hub in the current direction. Any clicking or ratcheting noise from the front wheels) is a sign the automatic hubs are not locking.. An Easy test is to get under your truck and rotate the front axle shafts (not the drive shaft).. Rotating the axle shafts by hand mimics 4x4 being engaged. After a few revolutions an Autohub should lock in and be impossible to turn.. If you are able to keep turning the axle it indicates the hub is bad/gunked up. For manual hubs the test would be to get under the truck with the HUB unlocked (4x4 off) and verify the axle shaft rotates freely. Next lock the hub, the axle shaft should be impossible to turn. If you are able to turn the axle it indicates the hub is bad/gunked up. Worn or heavily greased autohubs tend to buzz or chatter when going around corners (the hub mechanism is partially trying to engage). If you lock the hubs and the noise goes away then a good hub cleaning is in order. HUBs (automatic & manual) are insensitive to the electronic 4x4 system. The electronic 4x4 system only shifts the T-case in/out of 4x4 by means of an electric shift motor and 4x4 computer. The computer is used to determine the current position of the T-case selector shaft which will determine the course of action when the 4x4 Buttons are pressed. To clean see the repair info in my sig line or find threads like: Fixing/cleaning my automatic hub If the T-case is engaging (lights indicate 4x4), but the front end doesn't feel like its locked then one or more hubs are most likely blown. The easiest way to test hubs while the vehicle is still on the ground: To test for a blown Auto Hub; 1) Put T-case in 4x2 (disengage 4x4) 2) Crawl under the truck and rotate the axle shaft (any direction). After several revolutions the autohub should click and lock. If you can still rotate the axle shaft the hub is blown.. 3) Repeat #2 on the opposite axle shaft.. 2nd test for blown Auto hub 1) Put T-Case in 4x4 (engage 4x4 for 20' while going forward to give autohubs a chance to lock) 2) Put Transmission in park 3) Jack up the Left (driver's side) front tire and try and rotate the whole wheel (Counter clockwise). 5) Jack up the Right (passenger side) and try and rotate the whole wheel (Clockwise). 4) If you can move either wheel it indicates the autohub Failed to lock and is bad. *Do not reverse direction in this test as an autohub could be unlocked. Also pay attention to the direction of the rotation (if you rotate the wheel the wrong direction it will unlock and invalidate the test. To test for a blown manual Hub; 1) Put T-case in 4x2 (disengage 4x4) 2) Lock in the Hubs 2) Crawl under the truck and try and rotate the axle shaft (any direction). If you can rotate the shaft the hub is blown.. 3) Repeat #2 on the opposite axle shaft.. More on Automatic HUB engagement: When you engage 4x4 the front drive shaft will spin and send power to the diff and then to the axle shafts.. The axle shafts will begin rotating within each autohub; after a few revolutions the engagement cam will have idle up within the autohub and caused the autohub to lock. Once this occurs on both hubs the wheel with the least traction will get power and begin to rotate. :scratch: Let the above sink in for a minute.. If you try to free a vehicle by quickly going from Forward to reverse you can easily blow an auto hub.. When you reverse direction the axle shaft obviously spins in the opposite direction causing the auto hub to UNLOCK and then LOCK in the new direction.. Under low power this isn't a big deal, but if you're on the gas heavy it can definitely damage the hub... Manual hubs are either locked or open, as such they are unaffected by rocking a vehicle in the manor above.