The truck actuates 4x4 mode on its own (2017 2500)

[SimpolMike]

I have hopped on a couple other threads with people having issues with their 4x4 systems. Decided it was time to start a new thread.
My 2017 2500 4x4 decided to switch into four wheel drive, on its own, twice, at freeway speeds while towing on a trip a couple months back. There was an audible sound both times (not a good sound either). I disconnected the electrical connection leading to the front axle actuator to be able to get back home. I should mention the truck had 21k miles on it at the time. I explained the situation to the dealer and brought it in (front axle electrical disconnected) and SHOCKER!! -the dealer could not recreate the problem and refused to crack the diff housing. So i have done that at this point to prevent further abrasion. I filmed the clean pan i drained the diff into, along with the silver streams of oil when i cracked the cover and the subsequent silver sludge so i can use this for my conversation with the dealer. Ironically i drive about an hour to the dealer in specifically because they are out of town a bit and sell and work on a lot more trucks than the ones closer to the zoo here in Pugetropolis.
I am very interested in others who have experienced the “auto four wheel drive engagement” and what the situation was at the time. I have read a couple reports that people were towing, and i am wondering if there is not a common thread here with an electrical issue associated with towing that potentially effects the actuator. The more data we can consolidate the better. I have to state with 5-6 warranty related issues and a couple of them severe (like this one), i am losing faith. I always said i bought the Cummins and the Dodge came with it (2000 Laramie which has been a fantastic truck), seriously disappointed with the path this one is on. (Prior post of mine i listed my truck as a 2018, i was so po’d that my clutch / entire mechanism was faulty from the factory i listed the wrong year). I bought this before I couldn’t get a manual and when the rolling craptacular collection of computers all play nice, i love it. Just purchased my first extended warranty ever. If anyone has thoughts about other aspects of damage i should be assessing thoughts are appreciated. I need to do some more research on the locking hub mechanism.
Would also appreciate information on shop “manuals”.

 

[AH64ID]

Was that your first diff fluid change at 21K.

Ive read a couple threads about the CAD trying to engage on its own, but can’t recall a common culprit.

 

[crazy jerry]

i told you in the other thread but you dont listen. first of all there is no hubs. comprende. second of all just pull out the 4bolts of the cad fork and you can inspect how bad the collar and inboard axle are grinded. third is dealers are dumb as dirt and barely know what s lug nut is. 4th its probly the tcase position sensor sending a bad command to the cad fork

 

[sag2]

So are you saying the axle actuator tried to engage and it was grinding as you were going down the highway? Does the 4x4 work correctly now? There were situations years ago with the 5v supply that caused the transfer case to try and shift because the encoder was sending an improper voltage indicating a shift was requested. That should not happen any longer because the DTCM might see the transfer case reporting a shift, but the BCM would not see a corresponding shift request from the 4x4 shifter. The only way it should shift one but not the other is a shorted circuit to the axle disconnect control circuit. You need to find out if there are any fault codes stored.

 

[SimpolMike]

Thanks guys very helpful. (I am listening now Jerry - sorry i missed your other post). the 4x4 works, engages and disengages successfully and is truley engaged (as opposed to just believing the indicator lights). Sag2: Yes, highway speed, towing a trailer, and all of a suddent the a 4x4 indicator illuminates on the dash, followed by multiple error messages, (service 4x4) and an audible clicking / grinding noise coming from the front axle as i pulled off to a stop as quickly as possible. Physical inspection, shut the truck off, restarted, all messages gone, shifts in and out of 4x4, no noise, back down the road (surface streets at low speed) 30 min later back on the freeway, two mins after highway speed, same story and i disco'd the electrical to the front axle. Talked to service from the side of the road, they said "we replace that actuator all the time, no damage done" i tell him thats unlikely considering the noise i heard. I would agree with you regarding the messaging between the computers, i.e. it should not happen, but it did, twice. Thanks for the specific details. I am going to run some tests hooked up to my trailer if it does not reproduce without it and will continue to pull codes until something comes up.

 

[crazy jerry]

heres how these ram systems operate. in 2x4 the driver side shaft turns forward, turns spider gears and turns passenger side inboard shaft in Reverse. passenger outboard shaft turns forward. ring gear and drive shaft do not turn. when 4x4 is selected theres a electromagnetic clutch (like a ac compressor) in the top mainshaft of the tcase that engages and the chain, driveshaft, ring gear are instantly up to speed of the vehicle and the inboard shaft is now turning Forward. a second later the cad fork slides the collar and connects the shafts. yours is grinding because the half shafts are turning opposite. this why i think you may have a bad tcase position sensor. its thinking its in 4x4 and sending a signal to the fork but really the tcase is still in 2x4

 

[SimpolMike]

Great explanation Jerry, thank you very much.