4x4 issues - 1999 Sport AWD 4.0 SOHC

[BrianD123]

Hello i picked up a used 1999 Explorer Sport AWD 4.0 SOHC. The previous owner said the 4by auto was constantly locking up as if it was 100%. So he took the drive shaft out. the vehicle has been rear wheel drive for about 15,000km since. I put the shaft back in and can hear a loud noise while driving and sure enough it is acting as if it's in full 4x4. the selector nob makes noise and functions fine while going through the selections (lights on the dash come on and go off as you choose 4x4/4lo. so the shaft came back out the same day I put it in and here I am.

could it be bad sensors telling it the wheels are slipping and putting full lock to the front axle? if so where would I find these sensors?

is it possible that it is just stuck in 4x4 and the electric shift motor failed? if so what is the best way to test this?

thanks
brian

 

[BrianD123]

I have done some reading and found some possible causes . but still do not know where to find them or how to diagnose them. any input would be great.

- (hall effect) front and rear speed sensors.
- (4wd) control module.
- (PCM) powertrain control module.
- (TR) digital transmission range sensor.

checked the electric shift motor. it is functioning.