Rear Prop Shaft Vibration?

[Bob Marley]

2005 B6 A4 6 speed Manual

Getting an increasingly intense rotary pulsating vibration particularly past 30-40mph and higher on or off throttle that seems to be focused in the rear but also throughout the entire cabin. The chassis has 193k and likely all mounts and rear parts are original OEM.

Feels like I'm rolling over gravel

Changed rear tires & rims to test

No bearing noise

I'm suspecting the rear Prob shaft center support.

I can get some motion up & down side to side. But I honestly don't know how to gauge how much is too much movement ... but it definitely would seem to be the source if infact there is excess wobble there.

However the job is too expensive & involving to misdiagnose, so I'm trying to collect as much real world input as possible.

Thanks guys

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[VinnysS4]

You can rebuild the driveline yourself.... It's not too involved or too hard.
I would go to a shop and have them put it up on the lift. If it's that bad, you should be able to see it.

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[apriliapilot]

Just to check it, you can see it just laying under the car with a floor jack. Definitely the center support bearing. The rubber should look cracked and depending on how far gone it is, you might see open space through it.

[Bob Marley]

Thanks. It's really weird. Even at slow speeds I can feel the car limp or lunge forward up & down...and wobble as if I had a tire with a weird bulge.. it only increases intensity as I roll faster. On or off throttle. Doesnt matter.

The movement feels oscillating...as if something that is supposed to rotate in a perfect circle is now oblong...

So at slow speeds it feels more like a wobble. And higher speeds if morphs into intense vibration and unsteadiness as if going over a large gravel paved road at speed.

It is not focused in the steering wheel. I feel it in the seats. The rear view mirror shakes, shifter shakes etc...

Car doesnt pull and Alignment was just done for good measure.

I replaced front wheel bearings, tie rod ends & cv axles already for several reasons including thinking it was the inner joint that might have failed. No luck

I've pried and pulled on the rear inner CVs as well and cant really get any play at all that alarms me & all 4 boots are intact.

I can however get some pretty easy back n forth motion from the Prop shaft itself with 1 hand... up & down a bit also. Especially when manipulating it near the center support bearing. But again compared to how dramatic it feels inside the car the movement I get from the shaft doesnt seems to match up to me.. but I could be dead wrong this is uncharted territory for me

I sourced a used replacement Prop shaft for $160 shipped & complete will 99k miles (current shaft has 193k+)

Considering the ease of install of a whole shaft assembly vs trying to separate and rebuild my current one, I figure even if I'm wrong the investment was minimal and I can move on to another culprit

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[apriliapilot]

I get what you are saying about the slop not seeming to match up to what you are feeling, but it is. It really really is. I thought the same thing and actually cracked a shaft because I thought my tires were out of balance or I had a bubble in the tread face.
Just think about what that shaft weighs and then how fast it is whipping around under your car....

Dont buy one unless your shaft is bad/cracked. You NEED to do the Center bearing if you buy one anyway so you are just spending extra money.