The vehicle was shaking badly and making terrible noises when not at a consistent throttle. A u-joint on the front drive shaft had failed. I went ahead and replaced all three u-joints on that drive shaft however I did not replace the center ball/cup joint. After I reinstalled the drive shaft, the vibration was still present.

I then threw the front drive shaft in the garbage (recycled of course) and replaced with a new unit from a local shop. That finally took care of the vibration.

I tried to lubricate the ball joint on the rear shaft but unfortunately that u-joint won't accept any grease. It must be blocked internally. I thought about pre-emptively replacing the entire rear drive shaft but they are unreasonably expensive so I left my working one alone.

While I had the disco offline for so long I replaced a bunch of other parts. I think drained and refilled the front, center (transfer case), and rear differentials with oil

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Smll Med Lrg front drive/prop shaft is making a racket	Smll Med Lrg	Smll Med Lrg	Smll Med Lrg
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Smll Med Lrg flushed the brake fluid, the old stuff was absolutely black	Smll Med Lrg	Smll Med Lrg	Smll Med Lrg
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Smll Med Lrg	Smll Med Lrg	Smll Med Lrg	Smll Med Lrg front prop shaft was clearly replaced previously
Smll Med Lrg	Smll Med Lrg the movement on this carden joint was notchy	Smll Med Lrg	Smll Med Lrg
Smll Med Lrg	Smll Med Lrg	Smll Med Lrg there you can see the completely bad u joint	Smll Med Lrg
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Smll Med Lrg	Smll Med Lrg	Smll Med Lrg	Smll Med Lrg some signs of leaking around right rear hug
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Smll Med Lrg	Smll Med Lrg tried to lube rear u joint. Not successful	Smll Med Lrg drained and refilled front and rear differentials also	Smll Med Lrg
Smll Med Lrg replaced intermitten rear o2 sensor while I was under the car	Smll Med Lrg	Smll Med Lrg replaced the o-ring to address that leak	Smll Med Lrg replacing u joints on old shaft didn't eliminate vibration. Ended up replacing entire shaft
Smll Med Lrg	Smll Med Lrg got the new shaft from Colorado Drive Shaft	Smll Med Lrg	Smll Med Lrg new front drive shaft installed
Smll Med Lrg	Smll Med Lrg drained an refilled transfer case	Smll Med Lrg	Smll Med Lrg
Smll Med Lrg drain	Smll Med Lrg fill port