rear end vibration

I'm wondering if anyone has ever had a rear end vibration that they can't seem to track down. I've got a 2000 3.8, 10,000 km ago had all new front suspension components, new tires, new brakes, new rear shocks about 15,000 km ago. This vibration is evident when I look in the rear view mirror I can see small items shifting side to side. It's not road noise or a loose front end or bad tires. I've had an alignment done 8 months ago (though it was sort of there even after the alignment). I'm wondering about rear bearings? Has anyone had to change or repack these? I don't see too much about it so I don't think it's a usual thing. It isn't any violent shaking or anything and honestly nobody notices in my family except for me.

Any other thoughts?

I will assume you have checked for an out-of-balance tire, bent rim, etc.

A rear drum might be out of balance, or warped badly enough that it is hitting something.
A rear wheel flange might be bent, or the entire axle is bent.

I think on these vans, a typical wheel alignment does not involve the rear wheels, so such problems would go undetected.

Bad wheel bearings usually start a distinctive rumbling noise before they start to vibrate.

Hi: I changed both of the rear wheel bearings last winter in my Garage. They are pretty massive units (I think) for a Van. It was a straight forward job, took about 3 hours. I replaced the parking brake cable as well. The old wheel bearings had approximately 260K Kilometers (160K miles) on them, they actually weren't that bad, even then.
Terry

were you getting some funny vibrations too Terry or was there another reason for the replacement?

P

So tonight I was driving on the highway behind my wife (who was driving the 2000 windstar in question). You can see predominately on the driver's side the rear axle pulsating up and down when traveling on relatively smooth road. We're driving at ~100km/hr. As luck would have it, an identical windstar was driving along at one point and I was able to compare the axle motions between the vans and ours is definitely pulsating. Now I know the brakes are fine, the shocks were replaced ~10000 km ago, springs are OEM and the van has a total of ~140,000 km. Front end suspension was completely replaced and aligned by a reputable shop ~6000 km ago.

There is no typical "bearing" noise or grinding, cracking popping etc. The only symptom is within the van there is a slight "shimmy" at the rear end; the axle has this "hopping" vibration I described above.

Does this sound like the axle is bent? The van has never been in an accident and I'm the sole owner. I don't know what else it could be.

Thoughts? Has anyone ever replaced a rear axle on a windstar?

Piper

anyone??

How much tread is on that tire that is 'hopping'? I'm thinking an old, out of balance tire or bent rim could be your culprit. Easiest to change out with out gutting the rear axle. If you get sassy enough, try roating the tires and see if that tire bounces on it's new location or if a different tire in that location reacts the same. If the new tires reacts the same, I'm inclined to lean towards the bent axle or drum out of balance theory. If not, then I'd attribute it to the tire/rim. See how she rides after that. i'd love to hear how you make out.

One more thought...check the air pressure in the tire. It could be a tad low. I found a rough ride was corrected after getting the pressure up in each tire to it's spec pressure.

Mike

It seems to me that something must be out of balance. About the only culprits are the tire and the drum/rotor and hub. However, it could be a lug nut, a missing lug nut, or the wheel cover.

A quick inspection might be enough to get down to the bottom of it. You might ask to have the tire balance checked.

If this doesn't resolve it, and you've got some miles on the tire, you should be able to notice some tread wear variation around the tire. Look for the spot with the most wear, which will generally correspond to the heavier part of the tire. Use some nail polish to mark the rim and one of the lug bolts. Mark the surface of the tire in a few places with a grease pencil (or something else that would work). Remount the tire so that the hub mark and wheel mark are on opposite sides (144/216 degrees). Drive the vehicle a short distance (at speed) to wear down the grease pencil marks. Check for the hardest wearing spots. If the wear is still alligned with the marked lug bolt, then the problem is in the drum/hub balance. If it's moved with the tire, then it's the wheel/tire balance.

thanks for the suggestion guys. While I have gone thru the same thoughts you have along with diagnosing in a similar fashion I haven't turned up much. I'm going to get the tires balanced to make 100% sure it's not that. I hope it is as the next change (axle, trailing arm bushings) gets pricey. I'll keep you posted.

P

you could try rotating tires front to rear......if the rear tires are causing the vibration.....you will REALLY notice it on the front.......more so than on the rear.

Tires left on the rear of most any front wheel drive car can develop "cupping" or flat spots......which can cause a vibration.
It is much less noticable on the rear than on the front......but (as long as the alignment, tire ballance and suspension are good) the cupping wear happens primarily on the rear.