1998 Navigator NO low range

[rockinrolla]

Will recheck soon thanks for the help

 

[stamp11127]

I'm going to assume you did disconnect the switch from the circuit in order to check the resistance...

 

[rockinrolla]

I'm going to assume you did disconnect the switch from the circuit in order to check the resistance...

Yes

 

[stamp11127]

Are you able to get alligator clips on the connectors?

 

[rockinrolla]

Sorry everyone been out of town and have not been able to check i finally had time with alligator clips

2 hi 3080

4Awd 1505

4 hi 689

4 low 250

Still no low range how to test the brake switch? Thanks

 

[BIG GREEN FORD]

Sorry everyone been out of town and have not been able to check i finally had time with alligator clips

2 hi 3080

4Awd 1505

4 hi 689

4 low 250

Still no low range how to test the brake switch? Thanks

To see if your brake switch works press the brakes aand look at your tail lights

 

[stamp11127]

I'll look when I get home to verify but from memory the low range is controlled by the GEM in that certain conditions have to be met before it will shift into the low range. Rockinrolla send me your email address in a pm.

Update:
Transfer Case —Automatic Four-Wheel Drive (A4WD)
The automatic four-wheel drive A4WD system is an electronic shift 4x4 system that allows the operator to choose between three different 4x4 modes as well as two-wheel drive (2WD). The operator can switch between 2WD, A4WD, and 4WD HIGH modes at any 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.

In A4WD, the generic electronic module (GEM) varies the torque split between front and rear drivelines by controlling the transfer case clutch. The transfer case clutch allows for slight speed differences between the front and rear driveshafts which normally occurs when negotiating a corner on dry pavement. When the rear wheels are overpowered, the GEM detects this slip condition, and the duty cycle to the transfer case clutch is increased until the speed difference between driveshafts is reduced.

The 4WD mode switch is a rotary switch which allows the vehicle operator to choose between 2WD, A4WD, 4WD HIGH, and LOW range positions.

The vehicle speed sensor (VSS), mounted on the rear of the transfer case, informs the GEM of vehicle speed.

The Hall effect sensors, mounted to the transfer case, are used to detect the speed of the front and rear driveshafts.

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 2H/A4WD, 4WD HIGH, and LOW range positions.

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

The transmission range (TR) sensor, located on the left side of the transmission, informs the GEM of the transmission gear position.

The Expedition/Navigator is equipped with 2WD and 4WD vacuum solenoids attached to the upper RH side of the engine compartment dash panel, they alternately route vacuum to the vacuum motor which engages/disengages the center axle disconnect collar in the front axle assembly.

The 4x4 shift motor relay is a module containing two relays which, under the control of the GEM, shift the transfer case shift motor between the 2WD and the three 4WD modes.

The solid state clutch relay is used to activate the A4WD clutch within the transfer case.

The Vehicle Does Not Shift Between 4WD HIGH and 4WD LOW Modes Properly
A4WD mode switch/circuit.
VSS.
BPP switch.
Transfer case shift relays.
Transfer case mechanism.
Transmission range sensor.
GEM.
Digital transmission range (DTR) sensor

 

[rockinrolla]

To see if your brake switch works press the brakes aand look at your tail lights

the tail lights work wasn't sure if it was another circuit

 

[rockinrolla]

What should i check next? Gem maybe vss but the speedometer works do the shift relays go bad? Thanks in advance

 

[stamp11127]

If you still have the prints bedrck46 posted I would check the vss then the gem.