So I went to put my pickup (04 1500 with the 5.7) into 4x4 low the other day, put it in neutral, turned the switch then the "service 4x4" light popped up and I had no gears and had to shut the truck off to get it out of 4x4. Just confused as to why my 4x4 high works fine but 4x4 low won't engage? Any help is appreciated, this is my first dodge, and first half ton. I'm used to ford f250s

 

To shift into 4 Lo, the truck has to be stopped, the transmission has to be put into N neutral, and brake has to be released. So there is no load or binding on the drive train during the shift. Only then will the tcase shift in to 4 Lo with a very distinctive Click-Click-CLUNK. Same drive train set requirement when shifting out of 4 Lo. However, you can shift between 2 Hi and 4 Hi, "on the fly" at any time, meaning switch at will at any reasonable speed under 50 mph.

If stopped, neutral, no brake - and 4 Lo does not engage. Then is either an internal shift fork and mesh gear springs issue or an encoder motor issue. If you have the same setup as mine, the tcase is a NP243D