trying to find source of vibration

1.........Do you understand rotational clocking of the slip yoke? I cannot tell from that photo, but either of the caps on the one--piece part of the shaft MUST be "inline" just like rifle sights, if not, welded wrong

Also, the front joint behind the spline must ALSO be lined up with either cap inline with the very front joint. That is, they cannot be rotationally maligned say, 20, 30, 45, whatever degrees.

2.....I would spend some time, get it on jacks and see if you can tell anything by first watching the wheels and tires for wobble. You will want to jack it under the rear axle tubes to keep the weight on the suspension. Watch or have someone watch the wheels / tires for wobble and other out of true, and try and "feel" for shake

Then remove the tires and see if you can still feel it

3.....Spend some time gently and more firmly wiggling and feeling the rear bearings. This probably has the adjustable rear taper bearings, so there should be NO play

Here's a problem I had with mine that threw me for a loop. I had "thrown" in a temporary 3rd member. This is a Ferd 9" but it could happen to a Mopar

This pumpkin was an "open" (no limited slip) and soon began making weird noise, a little click or clunk ad 25-35 mph. It also made a strange noise on the highway. I probably only drove it 150 miles or less

Jacked up and "thought" I could feel plain in one tire AS IF THE FAR END of the axle was loose in the 3rd member.

Finally tore it down and that's EXACTLY what it was!!!!

Either the guy who had it was a "single track burn out king" or else a Jeeper / Mudder who liked to spin up the tires in mud

The side spider gear for that axle had been spun so much IT HAD WORN A CAVITY in the carrier!!!! There are no bearings in any of them, they are gear against carrier.

Anyhow just an example of "weird $sheet whut cun happen"