I got stuck in about 2in of sand yesterday in my 98 Ram 1500 4X4 yesterday. The indicator light for 4 wheel drive never came on, only right rear wheel was turning(front right was in a ditch), and no front wheels were turning in either 4Lo or 4High. What's weird, is that once I got on to concrete, I placed it in 4Lo, the truck crept at the low 4Lo rate, but still only power was coming from the rear wheels. Can someone with transfer case experience tell me why the truck will creep, but not provide power to the front wheels? No clunks or other problems, truck drives fine. I have had a slow leak from underneath, but I doubt that would be of major concern.

 

Your transfer case may not be the culprit. As a matter of fact, if you haven't looked at the vacuum lines and the CAD unit yet, the T-case most likely is not the problem, but rather the stinkin' vacuum actuator or a leaky line is preventing it from locking up.

Can you turn the drive-shaft by hand if your 4WD is engaged? If yes, look at the T-case, if no, look at your CAD.

 

Just long shot, but your CAD unit in your front axle may not be engaging. Easy way to test is put transfer case in 4wd on hard pavement, drive slow and try to turn. If the front end doesn't bind, chirp or resist in anyway, your CAD unit has not engaged.
Common problem is a vacumn leak but the diaphram could be shot as well. With the engine running, truck in park, and e brake on, (safety first) engage the transfer case in 4wd (doesnt matter low or high) and on the passenger side of the front axle, pull off the vacumn plug on the disk shaped diaphram. Should be strong vacumn signal (air) If so, I'd suspect the diaphram is blown. Check for air leaks, smashed steel line up by the T-case, and in rare occasions, the axle shiftsleeve is broke. You have to pull the axle apart for that. I suspect you have a cracked vacumn line or blown diaphram.
Good Luck! BTW you can search the forums for this as well.

 

transfer case is part of the drive line. think of it as having 3 major positions for the engine output. Hi range, neutral, and Lo range. so when you select 2hi or 4hi, you have normal (fast) gearing. when you select 4lo, you have slow (creep) gearing. additionally, 4hi and 4lo send a vacuum signal to the cad, which may or may not work. if it works, its locks the 2 piece axle and turns the wheels (and binds in a turn). if the cad doesn't work, then the differential just spins and does nothing, and you get stuck in sand.

 

I wanted to advise everyone that I found the culprit. I traced the metal vacuum lines to the plastic ones that enter into the diaphgram. There was one plastic line in the wire loom that had snapped. Good suction on the line though. I pulled the plastic lines from where they enter the diaphgram, and the side that enters the metal vacuum lines. Now, to take it to the dealership and hope that it is an easy and cheap replacement.

 

Yup. Pretty common. I think someone recently said it was only about $30 to replace the vacuum lines from the T-case to the CAD.