1999 f250 super duty crew cab 7.3 psd:

Would anyone know why my 4wd is engaging and disengaging by itself?

I recently had a vac leak which caused the HVAC controls to stop working and the ESOF stopped working also. I found a creak in the PVH solenoid and replaced it. I also replaced the 2 vac lines going from the hard line down to the hub. The HVAC controls work fine but now the 4wd is turning on and off when ever it feels like it. I have removed the selector button in the cab, disconnected the plug from the PVH solenoid, and even disconnected the vac lines from the hub. The problem still persists.

Any ideas?

 

How do you know the truck is going in and out of 4 wheel drive? Are you seeing or feeling something?

 

I am having this problem also, I have a 2000 f250 sd v10. My 4x4 quit about a month ago. and now when driving my 4x4 light on my dash will randomly come and go. The first time it happened I immidiately stopped and checked and my front axle spins freely so i know it was just the light flashing. I have since unplugged the tcase shift motor so it cannot try to go into 4x4 by itself. I have replaced the tcase shift motor, the gem, the switch on the dash and the relays under the hood. I have also checked all the fuses. Nothing has made any difference. I just rechecked all the fuses tonight and once again tried to shift into 4x4, nothing. Ialso have tried the test light at the tcase motor, under no circumstance am i able to get any current there, Any help would be great guys, as im about ready to douse it with gas and take a match to it!!!!!!!