4 X 4 does not engage front wheel drive when I move the 4x4 Shifter. Transfer case does shift into low range/high range ok, just no front wheel drive?

Which of these does your vehicle have ?

Transfer Case - NVG 233-NP1 (Two Speed Selectable)
Transfer Case - NVG 136-NP4(One Speed Automatic)

The New Venture Gear NV233 is an electronic shift transfer, with the following three modes of operation, Two-wheel drive high range, Four-wheel drive high range, Four-wheel drive low range. The gear reduction for low range is provided by a planetary gear set. The floor-mounted shifter has been eliminated. A switch, located on the upper right side of the instrument panel, is used to select the operating range. The indicator lamps on the switch show the current mode of operation. When the four-wheel drive has been selected, the four-wheel drive indicator lamp on the switch is designed to turn on when the front axle has engaged.


Automatic Transfer Case
The single speed automatic transfer case system shifts automatically from rear wheel drive to four wheel drive when the transfer case shift control module (TCSCM) senses the difference in rotation speed of the front propeller shaft and the rear propeller shaft . Two vehicle speed sensors, one located at the rear output shaft area of the transfer case, and the other, located at the front output shaft area of the transfer case, send front and rear propeller shaft rotation speed information to the TCSCM.
When the front and rear output shaft rotations remain the same, the TCSCM sends pulse width modulation signals to the encoder/motor to keep the transfer case in rear wheel drive. When the front and rear output shafts rotations are different, the shift control module sends pulse width modulation signals to the encoder/motor to engage the transfer case into four wheel drive.
The system will automatically transfer a percentage of torque to either the front or rear axles as required to stop all wheel slip. When the front and rear output shafts rotations return to the same speed rotation, the shift control module sends pulse width modulation signals to the encoder/motor to position the transfer case back into rear wheel drive.
When the transfer case is engaged into four wheel drive, a lamp indicator on the instrument cluster will light. The automatic transfer case system is completely automated, no transfer case control button switching system is required.

Do you know what diagnostic trouble code's are ?

DTC C0300 Rear Speed Sensor Malfunction
DTC C0305 Front Speed Sensor Malfunction
DTC C0308 Motor A/B Circuit Low
DTC C0309 Motor A/B Circuit High
DTC C0310 Motor A/B Circuit Open
DTC C0315 Motor Ground Circuit Open
DTC C0374 General System Malfunction
DTC C0376 Front/Rear Shaft Speed Mismatch
DTC C0550 ECU Malfunction
DTC C0611 VIN Information Error
DTC C0895 Device Voltage Malfunction

Not OBD2 engine code's .

Have it check for DTC'S - diagnostic trouble codes ?
GEM Diagnostic Trouble Code (DTC) Index
GEM Diagnostic Trouble Code (DTC) Index DTC Description Source Action C1728 Transfer Case Unable to Transition Between 2H and 4H GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. C1729 Transfer Case Unable to Transition Between 4H and 4L GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P0500 Vehicle Speed Sensor (VSS) Malfunction GEM GO to Pinpoint Test F . P1804 Transmission 4-Wheel Drive High Indicator Circuit Failure GEM GO to Pinpoint Test H . P1808 Transmission 4-Wheel Drive Low Indicator Circuit Failure GEM GO to Pinpoint Test I . P1812 Transmission 4-Wheel Drive Mode Select Circuit Failure GEM GO to Pinpoint Test E . P1815 Transmission 4-Wheel Drive Mode Select Short Circuit to Ground GEM GO to Pinpoint Test E . P1819 Transmission Park/Neutral Position Switch Short Circuit to Ground GEM GO to Pinpoint Test F . P1820 Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1822 Transmission Transfer Case Clockwise Shift Relay Coil Short to Battery GEM GO to Pinpoint Test E . P1828 Transfer Case Counterclockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1830 Transmission Transfer Case Counterclockwise Shift Relay Coil Short Circuit to Battery GEM GO to Pinpoint Test E . P1832 Transmission Transfer Case Differential Lockup Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1834 Transmission Transfer Case Differential Lockup Solenoid Short Circuit to Battery GEM GO to Pinpoint Test G . P1865 Transmission Transfer Case Contact Plate Power Short to Ground GEM GO to Pinpoint Test E . P1866 Transmission Transfer Case System Concern - Servicing Required GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P1867 Transmission Transfer Case Contact Plate General Circuit Failure GEM GO to Pinpoint Test E . P1876 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1877 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Short to Battery GEM GO to Pinpoint Test G . - For All Other DTCs GEM GO to Section 419-10 .
Your best bet , take it to a qualified repair shop that has the diagnostic tool to trouble shoot .
Principles of Operation
Transfer Case - Electronic Shift
The four-wheel drive, electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4X4 HIGH, and 4X4 LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators, one for 4X4 HIGH which is 4X4, and one for 4X4 LOW which is LOW RANGE (in 4X4 LOW both the lamps are on). Shifts into 4X4 HIGH can be made at any speed. When shifting into 4X4 HIGH with the vehicle stationary, tooth blockage may occur, preventing shift completion. When the vehicle is driven above 8 km/h (5mph) the shift will complete. When shifting in or out of 4X4 LOW, the generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission). (The digital transmission range [TR] sensor informs the GEM when the automatic transmission is in the NEUTRAL range position.)
The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and the range fork within the transfer case between the 4X4 HIGH, 4X4 LOW, and 2WD range positions.
The GEM uses two relays to control the gearmotor encoder assembly shift between 4X4 HIGH, 4X4 LOW, and 2WD modes. The GEM controls the pulse vacuum hublock (PVH) solenoid which supplies engagement and disengagement vacuum to control the hublocks.
The GEM accomplishes shifts by interpreting inputs from:

• mode select switch (MSS)
• vehicle speed signal (transmitted from the ABS system)
• gearmotor encoder plate position
• brake pedal switch
• digital transmission range (TR) sensor (automatic transmission)
• clutch pedal position (CPP) switch (manual transmission)
• ignition switch

Based on these inputs, the GEM controls the shifts into 2WD, 4X4 HIGH, or 4X4 LOW with the following outputs:

• low to high relay (clockwise)
• high to low relay (counterclockwise)
• pulse vacuum hublock (PVH) solenoid
• gearmotor encoder assembly

The electronic shift-on-the-fly (ESOF) system has a feature which allows the driver to override the vacuum operated hublocks. When the front hublocks are manually turned to the LOCK position, the hublocks are locked at all times, overriding the vacuum operated system. If the front hublocks are manually turned to the AUTO position, the hublocks can only be locked by turning the MSS to 4X4 HIGH or 4X4 LOW position.

did you turn the locks on the wheels, or check the fuses

Which do you have ?
Transfer Case - NVG 236 (Two Speed Automatic)
Transfer Case - NVG 233-NP1 (Two Speed Selectable)
The NV236 transfer case is an automatic transfer case with three drive ranges. Shifting from rear wheel drive to four wheel drive is done automatically when the transfer case shift control module receives wheel rotating slip information from the speed sensors. The transfer case shift control module then engages the transfer case motor/encoder to position the transfer case from rear to four wheel drive. When the transfer case shift control module receives information that the wheel rotation is the same on both axles, the transfer case shift control module sends position information to the motor/encoder to put the transfer case back into rear wheel drive. The three drive ranges are 2HI, 4HI, and 4LO. The 2HI position is for normal driving with the rear wheels pushing the vehicle. The 4HI, position is for driving through sand, snow, mud, gravel, or heavy rain at normal or slightly below normal speeds. The 4HI engages the front axle to allow for four wheel drive. The front axle is pulling the vehicle, and the rear axle is pushing the vehicle. The 4LO range is used for off road driving, heavy snow, deep mud, or shallow fording. The 4LO is similar to the 4HI except that the gearing in the transfer case is set for low speed and high torque. The NV236 is manufactured at Syracuse New York by New Venture Gear a division of New Process Gear for General Motors.
Is the switch light on or flashing ? If you have automatic 4x4 there are several DTC'S that can set >
DTC B2725 ATC Mode Switch Circuit Malfunction DTC C0300 Rear Speed Sensor Malfunction DTC C0305 Front Speed Sensor Malfunction DTC C0308 Motor A/B Circuit Low DTC C0309 Motor A/B Circuit High DTC C0310 Motor A/B Circuit Open DTC C0315 Motor Ground Circuit Open DTC C0323 T-Case Lock Circuit Low DTC C0324 T-Case Lock Circuit High DTC C0327 Encoder Circuit Malfunction DTC C0362 4LO Discrete Output Circuit High DTC C0367 Front Axle Control Circuit High DTC C0374 General System Malfunction DTC C0376 Front/Rear Shaft Speed Mismatch DTC C0387 Unable to Perform Shift DTC C0550 ECU Malfunction DTC C0611 VIN Information Error

It depends on what is wrong , is the 4x4 light flashing ? Are you aware of the complexity of the 4x4 system ? Has a electronic control module , has the ability to set an store DTC'S - diagnostic trouble codes !
Transfer Case The four wheel drive system is an electronic shift 4X4 system that allows the operator to choose between three different modes. The operator can switch 4X4 HIGH modes at any speed. To engage or disengage 4X4 LOW the vehicle speed must be less than 5 kph (3 mph), the brake depressed, and the transmission must be in NEUTRAL.
The shift motor sense plate, an integral part of the electronic shift motor, informs the generic electronic module (GEM) of the transfer case shift motor and contact plates A, B, C and D position.
The digital transmission range (TR) sensor is located on the LH side of the transmission, and informs the GEM when the transmission is in the NEUTRAL position.
The electronic shift motor is mounted externally at the rear of the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4X4 HIGH, 4X4 LOW and 2WD range positions.
When the GEM verifies the completion of the transfer case shift from 2WD to 4X4 HIGH (reading the contact plate positions), the GEM will then energize both pulse vacuum hublock (PVH) solenoids (supplying ground for 45 seconds). The PVH solenoid will allow a HIGH flow of intake manifold vacuum to the "wheel end hublocks", engaging the wheel end hubs to the front differential and transfer case to achieve four wheel drive.
Here are just a few DTC'S the system can set an store in the module !
P1804 4WD High Indicator Circuit Failure GEM GO to Pinpoint Test C . P1806 4WD High Indicator Short to Battery GEM GO to Pinpoint Test C . P1808 4WD Low Indicator Circuit Failure GEM GO to Pinpoint Test C . P1810 4WD Low Indicator Short to Power GEM GO to Pinpoint Test C . P1812 4WD Mode Select Switch Circuit Failure GEM GO to Pinpoint Test A . P1815 4WD Mode Select Switch Circuit Short to Ground GEM GO to Pinpoint Test A . P1820 Transfer Case CW Shift Relay Circuit - Failure GEM GO to Pinpoint Test A . P1822 Transfer Case CW Shift Relay Coil Short to Power GEM GO to Pinpoint Test A . P1824 4WD Electric Clutch Relay Circuit Failure GEM GO to Pinpoint Test A . P1826 4WD Low Clutch Relay Short to Power GEM GO to Pinpoint Test A . P1828 Transfer Case CCW Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test A . P1830 Transfer Case CCW Shift Relay Coil Short to Battery GEM GO to Pinpoint Test A . P1838 Transfer Case Shift Motor Circuit Failure GEM GO to Pinpoint Test A . P1846 Transfer Case CONTACT PLATE "A" Circuit Failure GEM GO to Pinpoint Test A . Now are you sure you really want to mess with this ? You would need a factory diagnostic scan tool to check this out before you start replacing parts !
Here

Manual shift or Four-Wheel Drive Systems - Electronic Shift I'm assuming you have electronic shift because you refer to relay clicking behind the instrument panel . Principles of Operation Transfer Case - Electronic Shift
The four-wheel drive, electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4X4 HIGH, and 4X4 LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators, one for 4X4 HIGH which is 4X4, and one for 4X4 LOW which is LOW RANGE (in 4X4 LOW both the lamps are on). Shifts into 4X4 HIGH can be made at any speed. When shifting into 4X4 HIGH with the vehicle stationary, tooth blockage may occur, preventing shift completion. When the vehicle is driven above 8 km/h (5mph) the shift will complete. When shifting in or out of 4X4 LOW, the generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission). (The digital transmission range [TR] sensor informs the GEM when the automatic transmission is in the NEUTRAL range position.)
The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and the range fork within the transfer case between the 4X4 HIGH, 4X4 LOW, and 2WD range positions.
The GEM uses two relays to control the gearmotor encoder assembly shift between 4X4 HIGH, 4X4 LOW, and 2WD modes. The GEM controls the pulse vacuum hublock (PVH) solenoid which supplies engagement and disengagement vacuum to control the hublocks.
The GEM accomplishes shifts by interpreting inputs from:

• mode select switch (MSS)
• vehicle speed signal (transmitted from the ABS system)
• gearmotor encoder plate position
• brake pedal switch
• digital transmission range (TR) sensor (automatic transmission)
• clutch pedal position (CPP) switch (manual transmission)
• ignition switch

Based on these inputs, the GEM controls the shifts into 2WD, 4X4 HIGH, or 4X4 LOW with the following outputs:

• low to high relay (clockwise)
• high to low relay (counterclockwise)
• pulse vacuum hublock (PVH) solenoid
• gearmotor encoder assembly

The electronic shift-on-the-fly (ESOF) system has a feature which allows the driver to override the vacuum operated hublocks. When the front hublocks are manually turned to the LOCK position, the hublocks are locked at all times, overriding the vacuum operated system. If the front hublocks are manually turned to the AUTO position, the hublocks can only be locked by turning the MSS to 4X4 HIGH or 4X4 LOW position.
Do you know what DTC'S - diagnostic trouble code's are ?
GEM Diagnostic Trouble Code (DTC) Index
GEM Diagnostic Trouble Code (DTC) Index DTC Description Source Action C1728 Transfer Case Unable to Transition Between 2H and 4H GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. C1729 Transfer Case Unable to Transition Between 4H and 4L GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P0500 Vehicle Speed Sensor (VSS) Malfunction GEM GO to Pinpoint Test F . P1804 Transmission 4-Wheel Drive High Indicator Circuit Failure GEM GO to Pinpoint Test H . P1808 Transmission 4-Wheel Drive Low Indicator Circuit Failure GEM GO to Pinpoint Test I . P1812 Transmission 4-Wheel Drive Mode Select Circuit Failure GEM GO to Pinpoint Test E . P1815 Transmission 4-Wheel Drive Mode Select Short Circuit to Ground GEM GO to Pinpoint Test E . P1819 Transmission Park/Neutral Position Switch Short Circuit to Ground GEM GO to Pinpoint Test F . P1820 Transmission Transfer Case Clockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1822 Transmission Transfer Case Clockwise Shift Relay Coil Short to Battery GEM GO to Pinpoint Test E . P1828 Transfer Case Counterclockwise Shift Relay Coil Circuit Failure GEM GO to Pinpoint Test E . P1830 Transmission Transfer Case Counterclockwise Shift Relay Coil Short Circuit to Battery GEM GO to Pinpoint Test E . P1832 Transmission Transfer Case Differential Lockup Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1834 Transmission Transfer Case Differential Lockup Solenoid Short Circuit to Battery GEM GO to Pinpoint Test G . P1865 Transmission Transfer Case Contact Plate Power Short to Ground GEM GO to Pinpoint Test E . P1866 Transmission Transfer Case System Concern - Servicing Required GEM CARRY OUT the electronic shift function test. REFER to Function Test - Electronic Shift in this section. P1867 Transmission Transfer Case Contact Plate General Circuit Failure GEM GO to Pinpoint Test E . P1876 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Failure GEM GO to Pinpoint Test G . P1877 Transmission Transfer Case 2-Wheel Drive Solenoid Circuit Short to Battery GEM GO to Pinpoint Test G .
Your best bet , take it to a qualified repair shop .

have truck running,,put shifter in neutral,,shift into high lock 4x4,then put truck into gear,,u can shift from high lock to high gear,,from two wheel to four wheel,,in high only,,if u want to shift transfer case in low,,u have to put truck in ,,neutral,,first,,

Electronic Shift On the Fly (ESOF) Operation
The ESOF system is an electronic shift 4x4 system that allows the operator to choose between two different 4x4 modes as well as 2-wheel drive. The operator can switch between 2WD and 4WD HIGH mode at speed. To engage or disengage LOW Range, the vehicle speed must be less than 5 kph, the brake depressed, and the transmission must be in NEUTRAL.

The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is used to spin up the front drive-line when shifting from 2WD to 4x4 High mode at speed. When the control switch on the instrument panel is turned, the generic electronic module (GEM) recognizes that a shift has been requested and activates the electromagnetic clutch and the relays which power the transfer case shift motor. When the shift motor reaches the desired position as determined by the contact plate position inputs to the GEM, power to the shift relays and motors will be removed. When the transfer case front and rear output shafts are synchronized, the spring loaded lockup collar mechanically engages the main-shaft hub to the drive sprocket. Finally, the front axle collar is engaged and the electromagnetic clutch is deactivated.

Shift Between 2WD and 4x4 HIGH:
Shifts between 2WD and 4x4 HIGH can be made at speed. Listed below are the inputs and outputs needed by the GEM to execute a change between any of these modes.

Feature Inputs:
*4WD Mode Switch (Various resistances).
*Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open).

Feature Outputs:
*4x4 Shift Motor Relay Outputs
*Transfer Case Clutch Relay (grounded when relay is on, open circuit when relay is off).
*4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).
*Cluster Indicators (ground when activated, open circuit when deactivated).

Shifting Into/Out of 4WD LOW:
When shifting into or out of 4WD LOW, the GEM requires that the vehicle speed be less than 5 kph, the brake is applied, and the transmission is in NEUTRAL.

Feature Inputs:
*4WD Mode Switch (Various resistances).
*Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open).
*VSS Sensor (Sinusoid Signal: 0.7V-20V, 2.2 Hz/mph).
Brake Input (battery voltage when brake is depress, open circuit when not activated).
*Transmission Range Sensor (grounded when transmission is in NEUTRAL, open circuit otherwise).
8Start/Clutch Depressed Input

Feature Outputs:
*4x4 Shift Motor Relay Outputs
*4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).
*Cluster Indicators (grounded when activated, open circuit when deactivated).

4WD Mode Switch
A rotary switch allows the vehicle operator to choose between 2WD, 4WD HIGH, and 4WD LOW modes of 4x4 operation.

GEM Module
The Generic Electronic Module (GEM) controls the operation of the 4x4 system

Vehicle Speed Sensor
The vehicle speed sensor (VSS), mounted in the rear of the transfer case, informs the GEM of the vehicle speed.

Transfer Case Shift Motor Sense Plates

The shift motor sense plate, an integral part of the electric shift motor, informs the GEM to the positions of the transfer case

Transmission Range Sensor
Located on the left side of the transmission, this sensor informs the GEM when the transmission is in the NEUTRAL position.

Electric Shift Motor
The electric shift motor, mounted externally at the rear of the transfer case, drives a rotary cam which moves the mode fork and range fork within the transfer case to select between the 2WD, 4WD HIGH, and 4WD LOW positions.

4x4/4x2 Vacuum Solenoids
These two solenoids are attached to the upper RH side of the engine compartment dash, and alternately route vacuum to the vacuum motor which engages/disengages the center axle disconnect collar in the front axle assembly.

4x4 Shift Motor Relay
A module containing two relays which under the control of the GEM, shift the transfer case shift motor between the 2WD, 4WD HIGH, and 4WD LOW modes.

Transfer Case Clutch Relay
An electromechanical relay is used to activate the transfer case clutch within the transfer case.

Good luck and hope this helps,but start with the simple and check the fuses and wire harness. Both white/light blue stripe wires should have 12V in run. The GEM will ground the left side (closest to engine) solenoid to disengage the front axle. It will ground the the right side solenoid (closest to fender) to engage the front axle. If the GEM doesn't see Neutral it will not let the truck come out of 4Lo. If the GEM had water leaking on it it may well be the root of the problem. The shift motor only has power when the GEM sends it a signal to move the shift lever. Once the shift is completed the motor shuts off. There are 2 wires that control the shift motor. A yellow and an orange. The GEM alternates between 12v and Ground to these wires to control which way the motor turns. The GEM uses the transfer case shift relay module to control the power to the motor. There are contact plates inside the shift motor assembly that indicate the position that the shift lever is in. This is what the GEM used to know what the T-case is doing. Any one of these components can fail.

You can try several things. You can stop the vehicle as if you are going into low range and shift the high range 2h, 4h, etc.. Ford advertises the Electric button type as "shift on the fly" but does not say the gears are synchronized to do that with manual engagement.

Change the lube this time to see if the lube is Milky. There have been floods, otherwise the case is sealed whether you park it or drive it. You still could have rust on the shift linkage. You need to move the linkage as you spray it. Then the offbeat chance something was bent from offroading. A Salvage Yard is a wonderful place to learn how a car is built. You may see their part looks different than yours.

You say 'new' truck, 09? or new used? I have had 3 Fords, 3 w/ manual trans. case, if you go into 4x4 Low range, you must come to a complete stop before shifting the trans. case to 4x4 mode, and I always put trans (automatic) in neutral before slipping into 4x4, it engages smoothly, no grinding. 4x4 high range can be put in while moving, but I would let off the gas pedal, shift to 4x4 high range, then resume accelerating. If there is any grinding going on doing it as above, something isn't right. Check the trans. case fluid level also, to make sure that's not an issue.