I just bought my 2001 Ram 1500 w/ a 5.9 yesterday afternoon. Didn't have a chance to test the 4WD at the time, so I did that today. It went into 4WD fine, and all 4 wheels turned, but it made a clicking/grinding noise the entire time it was in 4 high and low, but does not make any noise in 2WD. Any ideas what I might be dealing with, and/or suggestions on where to look to fix it? Thanks

 

read through this - http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm

most likely one of two problems, either:
no engagement, or poor engagement of the collar at the CAD, causing the 2 axle halves to slip and grind.
bad u-joint in front drive shaft, which only turns in 4wd.

 

Point of note - my 95 has a bad outer U joint on the front and was clicking and grinding, but it was happening all the time. The shaft on the 95 spins in 2 and 4 wheel drive

 

+1 on the front shaft.

 

the axle shaft spins in both 2wd and 4wd.

the front drive shaft only spins in 4wd (assuming that the CAD is functioning correctly and the collar is in the unlocked position)

 

Just an update to this in case anyone else has a similar issue; I found out what is ailing my 4WD. When it was in the shop for the tranny rebuild, my mechanic noticed the pinions or something in the front of the rear differential was loose that shouldn't be, so he removed my front drive shaft and left it off the truck until I am ready to address and fix that issue. I am not overly familiar with the parts to the 4WD, so a lot of that is kind of foreign to me compared to other mechanical things, but that is what he told me.....