I just bought a 02 ram 1500 quadcab. the only way I can drive it is when the floor shift is in 4x4 but only the two rear wheel engadge. when I shift into 2 wheel drive I hear a rattling from what sounds like the front differential. I think I have a NV241d transfer case and I followed the one hose from the transfer case and it runs to the fire wall and stops and it had a little plastic cap on it. it did not connect to anything. the guy who sold it to me thinks its the transfer case . has any one had this problem ? any input from you guys would be greatly appreciated.

 

Hose with the little plastic cap, is a breather hose.
As for the main issue of no drive in 2wd etc, get underneath the truck and see if when someone topside selects 2wd 4wd and lo, the lever is actually moving and solidly engaging in those positions.
The rubber gromets on these levers dry rot over time and even pop out and get lost.
Make sure all the hardware of this change lever under the truck, is actually there as it's common for them to fall off and get lost.
Also manually push the transfer case 2wd 4wd lo lever by hand. Get it fully engaged into 2wd by that method and try to move the truck.
If all is correct and in full working order, you'll have to dig deeper as the fault may very well be inside the transfer case.
Good luck and post up your results.
Al.