Hello, Long time searcher first time poster.

The truck is a 1998 ford ranger 4x4 electronic, manual, 3.0 engine.


I've been stuck 3 times now in a few inches of snow due to the lack of 4wd not engaging and would like to get this sorted out. I can turn the **** on the dash and the lights light up for 4wd and 4wd low and off. The fuse was blown once and I assumed that was due to the major puddle we drove into earlier in the week (that was the 2nd time we got stuck) after I switched the fuse the 4wd worked fine. Shut if off later in the day and it's not working again now. So I got stuck again tonight.

anyone have any good places to start? Could it be the switch on the dash? the motor that engages the system?

 

Welcome to the forum

Switch on dash is just 3 resistors and a ****, it is usually fine, 99.9% of the time

In 1998-2000 Rangers the GEM module behind the radio runs the 4WD system, it also runs wiper, interior lights, windows, door locks, ect....its the Body Computer
Then there is a 2 relay box behind the GEM, GEM uses these relays to operate the shift motor on the transfer case
If you changed Fuse #3, 20amp, in the Engine fuse box, thats the fuse for power to this dual relay box, which powers the Shift motor


Shift motor is the most common failure point, often because it sits unused for 10 months a year, you should shift in to 4low once a month, and back to 2WD just sitting in the drive way, don't have to drive it, just shift it, it keeps the motor working
You can often get it to work again temporarily by tapping on it to loosen dirty brushes inside the motor

Shift motor works like power window motor, if it gets +/- then window rolls down, if it gets -/+ the window rolls up, so polarity decide direction motor turn
Each relay in the dual relay box controls one of the wires to the shift motor
Each relay is a GROUND(-) when off, so motor has 2 grounds
When driver selects 4WD, GEM module activate ONE of the relays, which gives that wire 12volts(+) so motor now has +/- and moves
If Driver selects 2WD then GEM activates the other relay, so motor has -/+ and moves the other way back to 2WD

Shift motor and housing seen here: https://www.explorerforum.com/forums...-motor.123542/

In the shift motor housing is the Contact Wheel, pictures 5 and 6, it has 5 wires, this is how the GEM "knows" what position the transfer case is in at anytime.
When you select 4WD the GEM powers the shift motor to move in the correct direction and then waits for contact wheel to turn to correct position, then powers off the shift motor
GEM then turns on the 4high dash light
So the switch on the dash does not activate the dash 4WD lights, the GEM does but only AFTER shift motor's contact wheel is in the correct position

There is a brown wire at transfer case as well, it is for the electric clutch, it can't cause any issue with the system working it not

If Dash 4WD lights start to Flash that means GEM has tried to move shift motor and it didn't move, check fuse #3
If you don't hear the 1 relay "click" in the dash then relay box may be bad or GEM is
Check fuse #27 in the CAB fuse box

If 4WD light comes on the transfer case is in 4WD, if it doesn't feel or work like 4WD then one or both front hubs are not locked, its an OPEN differential so BOTH hubs need to be locked
1998-2000 Ranger 4x4s used PVH(pulse vacuum hubs) and they had a few issues, even new which is why Ford only used them for 3 years
Best to convert these to manual hubs, if they aren't already

 

Update:

After playing around and checking the shift motor and the modules behind the dash I decided it was best to mod the hubs and go that direction. Everything is working now as it should be.

Thank you for the assistance.