Drivetrain Hum and Vibration

dmtaurus

Member
Joined
Jul 1, 2012
Posts
42
I have an 06 Trailblazer LS with 119,000 miles. When driving the drivetrain is fine for about the first 3 miles at about 45 mph. After that distance, I feel a distinct low vibration or hum coming from the front end. Here is a little service history of things I replaced:

1. At 79,000 miles replaced struts with Monroe quickstruts and front wheel bearings with Timken brand units.

2. At 100,000 I replaced the rear driveshaft bearings with regreasable Moog u-joints.

3. At 119,000 I just replaced a really bad driver side outer end with a Moog brand part. When driving it would wander side to side a lot.

To diagnose, I have several questions.

First, does the front driveshaft turn when driving in two wheel? If so, I am thinking here that the u-joints may be going bad.

Second, since the tie rod end was really bad, probably for the last 8~10 months, the hub bearing was exposed to a constant force pushing in a direction towards the wheel, since the tire was always turned a little to the outside. The center area of the tire does show more wear than either side of the center area. So here I am thinking front wheel bearing.

The front cv joints appear to be in good condition with no grease leakage or torn boots. The tires are BF Goodrich and have about 59,000 on them. They have good treadlife left and don't have any bubbles or humped belts.

Any help would be greatly appreciated.
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Have you checked the front diff for proper fluid level? The large fill cap can be stubborn. Also make sure your disconnect on the right side of the oil pan is disconnecting the front driveline when in 2WD.

Are you driving in 2WD or are you leaving it in A4WD?

Just a note...always use 2WD when 4WD is not needed, A4WD will partially engage the 4WD system.
 
Does the hum change when turning or in a curve? That would indicate a bad wheel hub bearing.
 

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