4x4 diag

[Murdered_Ranger]

I've been trying to track down a 4x4 issue in my 99 ford ranger 3.0L. I am going to test the t case motor this weekend when I have some time. But my issue doesnt seem to be only the motor in my opinion. The light on the selector switch does not work and when I turn it I can sometimes here the solenoid in the GEM module click, but only when I turn the selector to 4Hi. Will replacing my t case motor fix that as well or do I need to look at a module as well?

 

[bobbywalter]

did you put it in neutral for low?

 

[RonD]

1995 thru 2000 Rangers do use the GEM as the 4x4 controller, GEM is in the the Radio cavity, on the side

There is also a Dual Relay box behind the GEM, that the GEM uses to power the shift motor
Shift motor is a 12v DC motor with 2 wires, and works the same as power window motors, it uses polarity, + and - on its 2 wires
12v-ground = window up
ground-12v = window down

The dual relay box has one relay for each shift motor wire, so 2, lol
When off both relays Ground their wire, you can test for this at the shift motor connector
The 20amp fuse in engine bay fuse box is connected to the dual relay box, it powers shift motor only
GEM only needs to activate ONE relay in the box to spin the shift motor, that one relay disconnects from ground and connects to 12volts from the engine bay fuse
Since the other wire is already grounded motor turns

Dual relay box rarely fails, and that's the "click" you hear behind the radio in the dash when activating GEM controller with dash switch

The other 5 wires on the shift motor go to the GEM, they are the position "sensors", contacts really
There is 1 control wire and then 4 position wires that are either connected to control wire or disconnected from control wire
If GEM can not tell the position of the shift motor, with key on, it should flash the 4WD dash lights, a few times after the key on bulb test, or it will flash the lights if you change dash switch and it doesn't know the position

By far the most common failure in this system is the shift motor, usually from disuse, not over use
The electric motor's contacts(brushes) and the position switch's contacts get corroded because they are never used
Always a good idea to shift from 2WD to 4High and then back to 2WD once a month just sitting in the driveway
You can do 4low as well but just for testing, spinning the motor and moving the contact wheel cleans all the contacts