Help me diagnosis a friend's problem

[SpeedingFirebird]

disclaimers: not my car, not an f-body. But it is a friend that watched my son for me over the weekend, so I told her I would help her out.

'07 Trailblazer. At highway speeds, out of nowhere, she gets a vibration in the seat and steering wheel equally. The amount of vibration is affected by speed. If she pulls over for 1 second and starts off again, it goes away not to return for a few more days.

Tires are fully inflated, no missing wheel weights. v6, auto, 4wd.

thoughts? I'm guessing a bad ABS sensor might be causing the ABS to drag a little after braking.

thanks!

[95redslp]

Re: Help me diagnosis a friend's problem

would something witht he torque converter be out of question?

[SpeedingFirebird]

Re: Help me diagnosis a friend's problem

would something witht he torque converter be out of question?

I was wondering about that myself, but I'm not a slushbox kind of guy.

[Meatyshells]

Re: Help me diagnosis a friend's problem

so she will just be driving down the highway at like 80 and it will just happen? Its not like a steering alinment type thing, or a driveshaft?

[josh98bird]

Re: Help me diagnosis a friend's problem

maybe driveshaft??? I have no clue

[bigbrian442]

Re: Help me diagnosis a friend's problem

The ABS is not active unless you are stepping on the brake.

2007 should still be under warranty.

Have you experienced the vibration or are you giving her description? More then one description can help.

I would first look at the wheel bearings or a lose wheel. Then check all the drive shafts and U joints. Does it have a steering damper on the drag link? IF it does and its bad this could cause it.

Brian

[silvachris1]

Re: Help me diagnosis a friend's problem

Is there a noise associated with the vibration? Just an off the wall idea. Could be the 4-wheel drive trying to kick in. I'm pretty sure the T-case is activated by a vaccuum hose. There's a *chance* that it could be related to that. Dad's beater truck started making some weird noises and his 4x4 light was on all the time. He unhooked the vaccuum hose and the problems stopped. Of course, now if he gets stuck, he's gonna have to hook the hose back up to get in 4 wheel drive.

[SpeedingFirebird]

Re: Help me diagnosis a friend's problem

Her and my friend described it to me. Yes, just going down the highway at 75 and starts to happen. Pull over, stop. Start again and it's gone.

Yes, it is under warranty. She was driving to my house from CT at the time and wanted to make sure it was safe to drive. I think she got an appt for Wed to have it looked at. Was just curious what it might be.

As far as guessing at the ABS, I was thinking maybe a light tap on the brake was causing a bad reading from the sensor. Stopping on the side of the road might reset it or something.

[silvachris1]

Re: Help me diagnosis a friend's problem

Well, like I was saying about the 4 wheel drive.... It was shakey and noisy (extremely noisy). We would slow down on the shoulder, and when we hit around 5mph, it would all go away. It was like the centrifugal force was throwing trying to force the 4x4 to engage, and when we slowed down, they disengaged. Kinda like a starter motor throws the gear outward.

[SpeedingFirebird]

Re: Help me diagnosis a friend's problem

Well, like I was saying about the 4 wheel drive.... It was shakey and noisy (extremely noisy). We would slow down on the shoulder, and when we hit around 5mph, it would all go away. It was like the centrifugal force was throwing trying to force the 4x4 to engage, and when we slowed down, they disengaged. Kinda like a starter motor throws the gear outward.

I asked, they said there was no noise associated with it.

[kristen]

Re: Help me diagnosis a friend's problem

wheels could always be off balan.

[SpeedingFirebird]

Re: Help me diagnosis a friend's problem

wheels could always be off balan.

that was my first though (hence I checked for missing wheel weights. However, the vibration is in the steering and chassis, plus it goes away when she stops. Both of those suggest it is not a wheel.

[HokieBird]

Re: Help me diagnosis a friend's problem

I looked through the trailblazer service bulletins and the only thing I could find that was remotely close was a torque converter shutter caused by water getting into the transmission.

[SpeedingFirebird]

Re: Help me diagnosis a friend's problem

I looked through the trailblazer service bulletins and the only thing I could find that was remotely close was a torque converter shutter caused by water getting into the transmission.

Interesting. Thanks Eric. I'll pass the info along.

[bigbrian442]

Re: Help me diagnosis a friend's problem

what did the problem end up being?


Brian