My '06 3500 is flashing and going into 4WLO without switching

Strange things began happening last night after changing the front diff fluid on my 06 3500. I drove home from shop, parked and turned off engine. I could hear the transfer case trying to go into 4WLO. Again engine was off and key out. I thought weird but ignored. Later last night I drove 15 minutes and parked, and again the sound. Just before turning off the vehicle, the 4WLO light display, but flashed only, as if attempting to go into 4WLO. I turned off vehicle and again heard the noise for about 1 minute. When it stopped I left the vehicle for approximately 10 minutes. When I returned and restarted the engine the car was flashing 4WLO and in 4WLO. Seems I could shift into 4W and 4WLO, but not 2W. When switching to 2W the 4WLO would again start flashing. Finally had to have truck loaded onto a flatbed and delivered to shop. Has anyone experienced or heard of this situation? What would cause the vehicle to want to shift into 4WLO whether engine is running or not, whether key is turned on or not? Any guidance would be appreciated.

 

Sounds like a short in the motor or the 4wd computer, or wiring, not common.

 

Thanks. Working on trying to trace problem. Seems like a short to us as well. Love the "not common" stuff. Makes life interesting.

 

That works on a 5v MUX circuit. Pretty sure I have previously done a good description of how it works. So it can be two things. One, the motor or (p)osition sensor is bad, or two, there is a short or bad sensor on the 5v circuit pulling the voltage down. When the voltage hits the right spot (lets say 4v=2wd, 3v=4wd, and 2v=4wd low) of 2v the transfer case thinks someone requested 4lo, and it attempts to make the shift.
Unplug the A/C pressure transducer first. Much cheaper than a shift motor.

 

Sure glad I have the manual stick to shove into 4wd. was looking at the 13's but with all the problems and no 4:10 unless dually, . . think I'll keep this.

 

My brother replaced 3 or 4 shift motors on his 03 DRW . It would shift into low as it sat overnight when it failed. This happened at approx 50-60K intervals.



Some history... ... ... when truck brand new he had a power enhancer installed (he can't remember what, but it plugged into harness under hood) At about 200K on a trip, truck started going from idle to governor by itself while idling at a rest stop. In an effort to fix he unplugged the black box system and put it back to stock. It cured the immediate problem... . and he never altered it from stock again. He also never replaced another shift motor and is now somewhere around 400K . He said the motor case is plastic and it looked as if the armature vibrated into the case?? I never saw it or the black box (he lives 3K miles from me). Sounds strange and if not my brother, might doubt what he was telling me. lol.

 

Okay turns out the actuator was bad. Replaced, seems to have fixed the problem. New question: is there anything, we could have done while servicing the front diff (cover off, cleaned, new fluid in, etc. ) that could have caused the actuator failure? I don't see how, but.....

 

No, no, and no.

 

Okay... lots of no's... . please explain. Are you saying the actuator wasn't bad (1st no)? Are you saying that replacing it is not the fix (2nd no)? Glad that a diff service didn't cause it.

 

The diff service most likely had nothing to do with the failure. If it is still good and was doing it all the time before, I would also have to say the motor fixed it.

 

Sag2... Thx for your responses. The actuator was actually frozen in 4WLo, how it happened beats me. Replacing seems to have been the right move. Trucks back on the road, time to hook up and go fishing.