Thread: Mystery vibration

If it is a uni-joint then driving it is dangerous, if a forward facing UJ lets go you could have a pole vault under your car, a rear UJ on the front T/shaft can destroy gearboxes and even brake lines on the chassis. If you have a vibration, STOP, and at least check it out, it could be anything from a UJ to a wheel bearing or even a wheel coming off, Regards Frank.

G'day Frank,
All your advice is sound should be well heeded, except the pole vault.
I watched the Mythbusters try over and over to make this happen. Even to the pointof dropping the shaft into a pole vault type receptacle and could only get the rear wheels to lift a foot or so off the ground.

Classic symptoms of uni joint failure, first one cup goes, then the opposite one. There should be a lot of looseness in one of the unis, find a level spot, chock a couple of wheels thoroughly and park the vehicle in neutral and handbrake off. Grab driveshafts and rotate them from the gearbox flanges.

Has it still got the rubber donut flange on the rear tail shaft (diff end)

As these wear and the only visible sign some times is bits or bit of string hanging out of it

Funny, my 300TDI auto started doing this driving back from Conjola the other day, vibrating on drive-on but not drive-off, it also has a scraping noise, but i think this is the serpentine belt, i also need to do a front swaybar bush, these will get done on monday, but if there is something else it may be i'd like to know, sounds similar to what i am experiencing, expecting it is the UJ

Originally Posted by Tank

If it is a uni-joint then driving it is dangerous, if a forward facing UJ lets go you could have a pole vault under your car, a rear UJ on the front T/shaft can destroy gearboxes and even brake lines on the chassis. If you have a vibration, STOP, and at least check it out, it could be anything from a UJ to a wheel bearing or even a wheel coming off, Regards Frank.

Yeah, sorry I was trying to be brief
I came off the freeway and stopped to have a quick look underneath but everything seemed OK and there was nothing immediately obvious that was loose or broken. When I then pulled away again was when it was really bad between 40-50k, but then after stopping at a couple of sets of lights it went away, so I carried on home.
I was about half a k from home when it started vibrating on decel instead of accel, but by then I thought I might aswell get home!
Haven't had chance to properly investigate, but it can wait till the morning now


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Originally Posted by rangieman

Has it still got the rubber donut flange on the rear tail shaft (diff end)

As these wear and the only visible sign some times is bits or bit of string hanging out of it

Cheers Rangieman,
Yep still got the rubber donut, it's relatively new though, replaced it about 18months ago.
Seemed to be OK when I had a quick look underneath, but will check it out properly in the morning


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Originally Posted by bee utey

Classic symptoms of uni joint failure, first one cup goes, then the opposite one. There should be a lot of looseness in one of the unis, find a level spot, chock a couple of wheels thoroughly and park the vehicle in neutral and handbrake off. Grab driveshafts and rotate them from the gearbox flanges.

Thanks bee utey, I'll give this a go in the morning.

Dan