a clunk under the cab when you go over bumps....I would think its gotta be a bushing..Stock Control arm bushings are a little harder to spot when bad simply due to there design and how they mount had this on my Grand cherokee and one of the most noticeable increases in the ride of it was replacing all of them. I later put in JKS Adj. CA's when i did the lift.

Bushings though is probably the right track....you can put it on jack stands but the amount of shock your trying to replicate (going over a bump) may be a little sketchy with it on stands..

...position wise lower ca's mount under the cab.

 

Check your slip yoke/tcase output for slop. Maybe U-joints too.

 

You could always zip tie a camera under the truck and hit some bumps so you can review the video for movement in places that it should not be. Have the camera pointing at one bushing, tie rod end, u-joint or ball joint per pass over a noise-producing bump.

 

I noticed last night my rear leaf spring bushings look very worn. Could this possibly be causing the rattle? I guess it could reverberate down the frame and feel like it's under the cab sometimes...

 

That could be it. If you have any way of getting the rear end off the ground with the axle not supported you might be able to see if you could make it clunk, but if they are worn you might as well just replace them.

 

I was going to put jack stands under the frame in the back and use a pry and floor jack to check them. That should work?

 

In theory it seems like it'll work.

Whether or not it will, remains to be seen.

 

In theory, the mechanic I took it to should have found the problem.... :0

 

Yes, but you must understand, while working on a Dodge, everything is 10x harder.

 

Try working on a Toyota or a Honda. There's one model car out there in the world that requires pulling the engine to change the spark plugs.