U-Joints and Vibrations?

[OneBadSkwerl]

Hey Guys,

I've been searching through some old threads to figure out what's up with my 1990 TSi AWD.

Between 120-140 (that's in km/h ) I have some pretty good vibration going it. It feels like a built in massager for my butt. The steering is fine so this leads me to believe that it has something to do with my drivetrain. I crawled under the car and grabbed the drive shaft around where it goes through the carrier bearings and I can give it a pretty good shake back and forth.

Also, I don't know if this is related but when I drive really slowly (5-10km/h) I hear a squack coming from underneath or the rear of my car. It sounds a lot like brakes squacking but my friend say it wasn't coming from the brakes. Could the worn out carrier rubber cause this or is my friend in need of some hearing lessons?

Also, when I'm cruising along and tap the brakes hard I hear a 'clank'. Just one clank. I assume this is the U-Joint. Sometimes as really slow speeds I hear clanks/ticks that are speed dependent coming from underneath the car. U-Joints?

Can U-Joints cause the vibrations I'm having at 120 or is it likely to be the carrier bearings? Could the tick at low speed be the U-Joints?

My tires are balanced, no ice in the wheels.

Sorry for the novel but thanks in advance.

Scotty

PS - Sorry, I posted this in the drivetrain section but I just realized it's probably more appicable in this section. My apologies.

 

[Doug99RS]

It sounds like you have a good grasp on the problem but you just need some re-assurance. To me, I think it might be your U-Joints IF there is in deed play in them. Let me see if I can't draw up a picture here for some assistance. You'll want to hold one side of the u-joint station and then twist the other. You may have already done that but I just want to make sure we are both on the same page. If you've got any play there then you'll want to replace them.

Bad u-joints will create a constant vibration, creaking noise on initial launch and brake application and when turning. You may want to see if you can spray some wd-40 in to the joint to see if you can change the condition. The wd-40 or anything else is not to fix or prolong the inevitable. It's simply to make a short term (one drive cycle) change to help diagnose the problem.

One other thing you may want to consideris bent wheels or tire hop. A balancer will put the wheel in balance but you'll actually have to watch the tire as it spins to make sure the wheel isn't bent and the tire isn't egg shaped. Just to throw that out there but I think with the noises it's probably not tire/wheel out of roundness.
Doug

 

[OneBadSkwerl]

Hey Doug,

Thanks for the response, that picture was awesome I've got a 'fairly' good idea but I've never had to do any drivetrain work so I'm fairly unfamilary with it.

I have already tried seeing if there was play in the U-Joints, and there was. I can hold onto each side and if I twist in opposite directions I get some play and if I twist really hard I can make a clink noise I know this means my U-Joints are pooched but would they be the cause of my vibratations only between 120 and 140? I don't notice anything at all under 120, fairly smooth ride.

Could the clank noise at low speeds be my U-Joint and the shudder between 120-140 be my carrier bearings? Is it possible that squack is coming from the carrier bearing rubber?

 

[Doug99RS]

While the example car is different, it's still a U-Joint issue. My 74 duster had u-joints that went out. They created a horrible vibration throughout the entire car. While mine was constant and changed with speed I'm sure that if I had known alot about cars back then, I would have known to look for a few signs BEFORE the catastrophic failure that really brought it to my attention.

On the Jeeps I've worked on, clunking, shimmies, and all kinds of noises came about from bad u-joints. If you know the joints are bad, I would replace them first before addressing any other noises. If the labor is double/difficult to replace a second suspected component and the part is cheap enough then I'd replace it too.

I try to start out cheap and obvious and get more expensive from there.