4WD light

A blowed bulb maybe? I've had to replace mine before.

what he said those little lights dont last forever

Corroded connection to the switch would be my guess.

my light quit working. on the back of the front axle, slightly toward the passenger side of the middle, there is an electrical connector to the CAD thing. mine was about 1/2 loose. I unplugged it and dumped a bunch of sand and mud out, sprayed in wd40, and poked around each hole gently w/ small screwdriver to scrape out more mud, sprayed in more wd40 several times. plugged it back up and it worked fine. you can test for voltage out on these wires and also test the switch on the CAD thing to see if its opening and closing (continuity vs no cont). Its probably just dirty. good luck.

Probably 4WD indicator lamp

A couple of years ago I had the same problem with my 98 1500 QC 4x4 5.9. The 4WD light did not come on but the truck seemed to be going into 4WD OK. I checked the indicator lamp switch on the vacuum shift motor and that was working OK, so concluded it must be a problem with the dash lamp. Disassembled the dash and removed the instrument cluster. Turned out the bulb was OK but the bulbholder, which is a friction fit in the printed circuit board, was not making good contact and so the 4WD bulb did not light. I swapped around a couple of bulbholders, tested with a multimeter and put everything back together. 4WD light has worked fine since.

There's some good info. on the 4WD front axle at dodgeram org - Diagnosing 4WD Engagement Problems