Rumble when deceleration

[Perspective]

My 06 Liberty auto with 241,000 miles just started making a new noise. It only occurs when I am decelerating and seems like it's about to downshift into 2nd and then again before going into 1st. When it gets close to down shifting into 1st, it also give a shake/shutter that you can feel. The sound is similar to engine braking in a manual.

Other than that, it seems to drive fine and shifts smoothly going up through the gears. This only occurs when slowing down.

Any thoughts? Would ****** mounts cause this? U joint? ****** going bad?

 

[KJowner]

Is there plenty of oil in the gearbox? Is it still nice and pink? If it's brown or black the clutch packs are slipping.
Start with the cheapest part after checking the oil, the front prop UJ, is the small rubber boot still in place? If not the joint is probably wrecked. You can completely remove the shaft for a test run, and the joint is cheap + easy to replace.

 

[Perspective]

So the gearbox oil is pink. The small boot coming out of the transmission on the drive shaft going to the transfer case is torn and there is definitely a little play. Looks like I'm starting there.

Any recommendations on where to purchase the kit for the front driveshaft? Rather not buy an entire driveshaft.