Intermittent Front End Vibration After Hitting Bumps

jeffreyjpa

Original poster
Member
Jun 7, 2013
1
First time posting on the new site, looks great! I looked through the past postings, and unfortunately didn't find one that matched my current problem.

We are having an intermittent issue with our 2002 Trailblazer LT 4x4, and I'm hoping someone can point me in the right direction. After I ride over even a small bump/pothole in the road, the front end makes a whirring/rattle kind of sound and I can feel a vibration until I slow down to a stop, then it goes away until the next bump. I can best describe the sound/vibration as what you would hear and feel if you were driving over a rumble strip on the shoulder of a highway or approaching a toll booth. It almost feels like I am dragging a small branch under the front of the car.

It first started about six months ago, but it was very intermittent, until about a week ago. I guess it could be in the front suspension or the wheel assemblies, but to me it feels like it is in the 4x4 system, which is why I posted here. And, I couldn't swear to it, but it seems like it is coming more towards the passenger's side.

Any ideas? Thanks!
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Welcome!

Ideas? We got PLENTY of ideas. :wink:

How many miles? Assuming you've been keeping up with the 50K fluid change interval on the transfer case (very very important), when was the last time you checked the fluid level in the front differential? Change its fluid at 100K?

A passenger side noise may also be the splined disconnect where the CV shaft meets up with an intermediate shaft that goes through the oil pan from the differential. It has a high failure rate after 100K miles or so from failed seals that allow the bearings to die. Check for play at the CV shaft inner "tripot" joint where its shaft goes into the splined disconnect.

For more reading: Offroadtb.com Front Axle 4WD Disconnect

Could also be a deteriorating wheel hub bearing.
 

northcreek

Member
Jan 15, 2012
3,300
WNY
the roadie said:
Welcome!

Ideas? We got PLENTY of ideas. :wink:

How many miles? Assuming you've been keeping up with the 50K fluid change interval on the transfer case (very very important), when was the last time you checked the fluid level in the front differential? Change its fluid at 100K?

A passenger side noise may also be the splined disconnect where the CV shaft meets up with an intermediate shaft that goes through the oil pan from the differential. It has a high failure rate after 100K miles or so from failed seals that allow the bearings to die. Check for play at the CV shaft inner "tripot" joint where its shaft goes into the splined disconnect.

For more reading: Offroadtb.com Front Axle 4WD Disconnect

Could also be a deteriorating wheel hub bearing.

Roadie...is the disconnect the same unit for V8 & I6 ?...Mike.
 

tblazerdude

Member
Dec 4, 2011
321
the three most common sounds over bumps are the hood, the front bumper, and the front end links. Roadie's post is also essential, but these three things are very easy to confirm and check. Plus any one can fix them.

Step 1. Try to lift the hood with out releasing the cable. Pull up hard on the hood. Push down on the hood just as hard. There should be absolutely no play or movement. If there is, There are screw type rubber bushings under the hood to the left and right of the radiator. You can adjust them to a tighter fit.

Step 2. Go to your front bumprer and try to move it up and down and left and right. If it is firm and has little to no movement you are all set. If you can move the bumper up more than 1/2'' then you need to inspect your plastic bumper brackets. There are two very fragile bumper slot pin brackets on either side of the bumper and they easily get dislodged or broken. It is the most common reason for bumper sag. Broken or loose brackets can also allow for the bumper to bounce over bumps thus causing a banging sound or loose rattle.

Step 3. Look under the truck, inside the front wheels. There is a bar that connects the two sides of the suspension, and it is connected through a set of links with rubber bushings. Grab the sway bar end link and try to rotate left to right. If you can rotate it, easily, it is nearing time for replacement. Any loose play and it is shot. If it has adequate to firm resistance then you are good to go.

Step 4. Look into what roadie is saying. The splined disconnect is a fickle thing.
 

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