Front axle not engaging????

I think I had my first issue with the new-to-me truck... I was backing the car trailer up a fairly steep and somewhat icy driveway in 2WD and the rear wheels started to spin. No problem, right? Put it in 4 and it sure seemed like the front wheels were not engaging, but I wasn't sure... I got the trailer where I needed it and blew it off... I get home and back the trailer into it's uphill spot. I'm in 4Low, I get it where I want it, I'm 95% sure that I put the funny knob in park and the truck ROLLS AHEAD!!!! I get out this time and look. 1 rear wheel was on ice... WTF?!?!?!? Obviously, this could be user error, but it sure doesn't seem like it to me. In the driveway with the car trailer, not a big deal.... On a boat ramp, BIG DEAL!!!

I was wondering if I should visit the dodge dealership before the warranty runs out.... I guess I know now... what says the experts? Any known front axle engagement issues???

What model truck? 1500 Bighorn, express, etc.
Do you have the 4 auto option or just 4low, 4hi, 2hi?
It could easily do that in certain models and without LSD rear.

Sounds more like a transfer case thing than the front axle. There are 2 different transfer cases -
1. is like a traditional transfer case and locks the front and rear wheels - 44-45 model and only has 2wd, 4hi, 4low as the options.

2 is an AWD type and uses clutches and does not engage until rear wheel spin is detected 44-44 model and has 2wd, 4 auto, 4 lock, 4 low options. However 4 lock is still not like the 44-45 transfer case and I do not know if it will engage when in park in any mode.

And of course there is the front axle actuator - but it seems to be fairly trouble free for the most part, but like any part it can fail.

With the BigHorn, you most likely have the BW44-44 transfer case, this can be verified by the "Auto 4X4" button. As explained in the post above, the transfer case (more accurately front drive) does not stay engage all the time when in any 4X4 mode. Your not even in the first 10K people to say "well that's F'n stupid". The front axle drive is basically driven by a variable clutch.
Give @Brandon-w a PM and ask about his lock up switch for this transfer case. I think he has options to keep the axle locked in Park/trucks off and to keep the front axle from engaging in Low range.

As the previous posters have mentioned if your transfer case has the auto function it does not lock up solid like an old style.
On my Bighorn when you place it in park it totally shuts off the transfer case front drive, I am not sure what it does to the front axle disconnect.
I have installed Brandons switch, what I do now if I stop someplace were I want to keep the 4wd fully engaged is.
With the switch activated and 4wd hi or lo activated I leave the truck in reverse or drive and set the parking brake,
it has not taken off on me since doing this in slippery situations.
Do I recommend this nope, but it's what I do as a bandaid on RAMs stupidity.

WOW! That is dumb... Yes, it's a BigHorn with 2WD, Auto, 4Hi and 4Lo. I know a little about older Jeep 4x4 systems but nothing about these.. Is the front axle disconnect on the Ram just an actuator that slides a collar like a YJ? If so, I'll guess it's not vacuum anymore but electric. Easily solved, but then there's the TCase and some clutches that need to stay engaged. I presume this is the Brandon fix.

How man Rams end up in the water at boat ramps? I could see this easily happening... Rear wheels are on slimey surface when the tide is out, front axle not engaged cuz there's no wheel spin or the truck is shut off. Truck trailer and boat go into the water. Even if the Ebrake was set, that's only the rear wheels even on a 2017, right????

hmmm... an easier solution might be a line lock on the front brakes used in conjunction with the stock Ebrake... Not sure if LLs even work with ABS since the last one I installed was on a 1970 442.

You don't even have to go back to an old school Jeep set up. The other transfer case offered in these trucks is the BW44-45 which is Part-Time style like the old Jeeps.
It is possible to swap in the BW44-45 transfer case to your BigHorn. You just need a donor transfer case, the switch on the dash that doesn't have the Auto button and AlfaOBD to change the BCM

A tcase swap on a pretty new truck isn't terribly enticing to me.. of course, sliding down a boat ramp isn't either... I did just go out and verify the front axle is really engaging since I had my doubts... And it does engage.. I see a product called BurnBox RAM that supposedly can lock the front brakes by tickling the ABS via the OBDII port... anyone used this thing? https://www.zautomotive.com/product/burn-box-ram/

Haven't used it but it does sound very interesting

Why not just get Brandon's switch, then you'll have the benefit of true 4-wheel drive while backing and not waiting for the rear wheels to slip enough to engage front end.
Just a thought!