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Discussion Starter · #1 ·
I have had my 2002 Astro AWD now for almost 2 years, and I have been chasing a vibration that is driving me nuts. It is a high speed 60 MPH and above vibration that seems to cycle every few seconds. It vibrates at highway speeds 60 and above, and when I lift all 4 wheels off the floor and run it up to highway speed, I feel the same vibration.
I have spent a small fortune trying to figure this out, but have gotten nowhere with it. These Are the things I have done:

* 4 new Michelin tires, balanced 3 times over. Costco hates to see me coming now.
* Had the rear differential completely rebuilt with new bearings.
* New rear wheel bearings.
* Had the drive line balanced by 2 very reputable balancing companies.
* New Universal joints
* Balanced rear drums and front rotors.
* New Transfer case rubber mount.
The vibration doesn't really feel like tires or wheels. It feels more like something at a higher frequency. Any ideas about what could be causing this would be greatly appreciated.

One thing I did notice when I was idling it along slowly in 1st gear on blocks, I noticed the front axles seem to run out quite a bit, but I cannot feel any slack in the joints.
 

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Do you feel it in the steering wheel or in the seat of your pants? In the steering wheel means something in the front end. Seat of the pants is rear or possibly frame/body.
 

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Discussion Starter · #3 ·
I can feel it in the steering wheel, but it also seems to rumble the whole van and create that rumbling noise like you're sitting in a big drum.
 

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You mention having the drive line balanced but have you ever tried taking out the drive shaft, and moving (rotating) the yoke in the transfer case by a couple splines. Do this all the way around.

I've seen a few cases that the vehicle is hitting a resonating frequency. sometimes taking part of the spinning parts, a little out of phase, can quiet a pesky "vibration". Especially if it's one that seems to be at very specific speeds.

Also you mention it may be worse when your vehicle is up on jack stands? are you lifting by the body or by the axles? If you are letting the axles and running gear hang, you are changing the "phase" by not having the springs loaded. It's also possible that the slight undulation of a highway can cause a loading and unloading of the running gear and changing the resonating vibrations. This might be why when you reach 60mph, your vibration seems to come and go.

DC
 

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The other place could be your CV joints/half shaft/axles in the front. if these or your front hubs are a little out of balance you would feel these in the steering wheel as well as the whole vehicle.

You mention them balancing the wheels/tires but not necessarily the hubs or front end components. You might want to put the vehicle up on jack stands (make sure they are real solid) and sit the vehicle on the control arms in front, and the axle in the back. Then have a friend bring the vehicle up to freeway speeds. See if one of the front wheels looks like it's shaking a bit more than the others. Try turning that wheel on the hub one or two lugs at a time and repeat. They could be just out of balance enough to create a vibration. Maybe the combination of the tire, wheel and hub are such that they all line up to be out of balance enough for you to feel it at 60mph. It would be like turning and balancing a tire on the car.
 

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This is mt first set of tires I had on mine that did not do anything at all. usually I had to fool with it for a long time to get rid of the issue with new tires.

Guy said he balanced them twice. Static and dynamic.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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Torque converter?
Rule out engine related vibration.. put vehicle in neutral at highway speed and see if vibration remains.

* Drivetrains typically hum
* Wheels typically shake

The vibrations are usually different
 

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Discussion Starter · #8 ·
I have balanced the front rotors and the drums on the rear.

I did try putting it in Neutral at highway speed and the vibration remained.

I have it lifted (All 4 off the garage floor from the frame) with suspension hanging. I'll put jack stands under the suspension and try that, but it didn't seem to make any difference last summer when I tried that.

Is there an in vehicle test to see if it's the torque converter (other than putting it in neutral at vibration speed)?
 

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Oh man, this sounds like the nightmare I went through with mine.
Mine was doing the exact same thing, rumble/vibration at freeway speeds, oscillating through the body every few seconds, sounds like its from the back....but it's not.

I did everything to mine, all new rubber mounts on everything - engine, trans and all the suspension, rebuilt front and rear diffs, new front axle shafts and front wheel bearings, new harmonic balancer, 3 sets of tires and 3 sets of rims all road forced balanced, new front driveshaft, rear driveshaft rebuilt and balanced like 5 times and nothing helped.

GM had a TSB out on these vans called the "rolling boom noise" I even found nos GM vibration dampers they called for in that TSB for the leaf springs and rear pinion nose, didn't help.

Then I discovered my rear driveshaft was missing it's harmonic balancer on the front,
This guy


I got a new yoke with balancer, installed it, had it balanced and the rumble/vibration was reduced by at least 85% but it was still there if you listened for it.

What cured the rumble/vibration 100% was when I replaced the engine. After I tore the old engine down I found #3 and #5 exhaust valves were leaking.

The only thing I can figure is the leaking valves were setting up some kind of resonant vibration that was being transmitted down the driveline and up into the cabin through the rear.
I've had LOTS of vans, but these vans are like little resonance amplifiers, I don't know if its the shape, size or what, but they pick up any vibration and amplify it.

So long story short, I feel your pain!!!!
My question is:
Hows your driveshaft harmonic balancer? You do have one, right? How well does the van idle?
 

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Discussion Starter · #10 ·
Yes, the harmonic balancer is there. I also had the drive line balanced by 2 different shops with good reputations. The sad part on this is the fact that I have invested a lot of money into this Astro including:
New tires
New Battery
3 Plus 1 lift kit
Roof Rack
Rear Ladder
New Full sized Rubber Matt in the rear
Custom built folding Couch / Bed
Jack (Best digital TV antenna available)
24" Samsung HD TV in rear
Custom Counter
Complete tune up including new spark plugs, Rotor and Cap, Wires

I am almost at the point of throwing in the towel on this one. I don't like defeat, but I have stressed way too much on this thing. Maybe it's just time to get rid of it. Someone make me an offer. It has 195,000 miles on it.
 

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I know the feeling, I almost gave up on mine many, many times!!!

How are the motor mounts, original? Does it have any kind of rough idle? Have you drove it with the front driveshaft removed?

Its frustrating, trust me.

All I know is when I get my next Astro/Safari, if it has ANY kind of vibration or rumble to it I'm walking the f*** away!!!
I don't care if it's a one owner rust free van with 15k miles and they want $200 for it....I'm walking! not worth it, lol!
 

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Discussion Starter · #12 ·
The motor mounts seem solid when I checked them by prying up on the block with a pry bar. It purrs like a kitten especially after the complete tune up. I drove it without the front drive shaft, but that didn't make any difference. I appreciate all your input.
 

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Here is the GM bulletin about the Rolling Boom Noise.
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Rolling Boom Noise Inside Vehicle (Install Pinion Nose Damper and/or New Rear Leaf Spring Dampers) #00-03-09-001B - (Oct 19, 2004)

Rolling Boom Noise Inside Vehicle (Install Pinion Nose Damper and/or New Rear Leaf Spring Dampers)
1995-2005 Chevrolet Astro Van Models

1995-2005 GMC Safari Van Models

This bulletin is being revised to add the 2005 model year, change a nut part number within the spring damper kit and change a quantity in the Parts Information. Please discard Corporate Bulletin Number 00-03-09-001A (Section 03 - Suspension).

Condition

Some owners may comment about a "boom" noise inside the vehicle while driving at speeds ranging between 97-105 km/h (60-65 mph). This condition is most noticeable from behind the driver's seat.

Cause

The condition may result from an engine-firing harmonic, which becomes noticeable at torque converter clutch (TCC) lock-up.

Correction

A new rear leaf spring damper kit (containing two dampers , one per spring) has been developed, to be used in conjunction with a pinion nose damper tuned to 86 Hertz (Hz), to reduce the resultant noise level.

AFFECTED VEHICLES MAY REQUIRE THE INSTALLATION OF THE PINION NOSE DAMPER, THE SPRING DAMPERS, OR BOTH. THE INSTALLATION OF EITHER OF THESE DAMPERS IS AT THE DISCRETION OF THE TECHNICIAN FOR BEST RESULTS. Use the following procedures and the appropriate part number listed below.

Important: Installation of these dampers will not totally eliminate the boom noise. The boom noise may only be reduced to a more acceptable level. There may be other boom noises, such as body or exhaust, associated with the vehicle and this fix may either diminish or enhance the noise. These other noises should be addressed prior to the correction for the TCC boom dampener being installed.
 

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You could always take it a frame shop and have them shoot it and see if everything is within spec.

I talked to a frame shop when I was going through this with mine and they said if there is something tweaked (if its been hit in it's past) it can cause what you are describing, they said doesn't take much. Its worth a shot.

When you had it on jack stands did you have the front driveshaft removed? When I tested mine on stands I removed the front driveshaft and just raised the back, that way I could totally rule out the front since it was sitting square on the ground.

Have you tried using a mechanics stethoscope to pin point the noise?


It did help localize the area on mine.
 

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1lowcab said:
You could always take it a frame shop and have them shoot it and see if everything is within spec.

I talked to a frame shop when I was going through this with mine and they said if there is something tweaked (if its been hit in it's past) it can cause what you are describing, they said doesn't take much. Its worth a shot.

When you had it on jack stands did you have the front driveshaft removed? When I tested mine on stands I removed the front driveshaft and just raised the back, that way I could totally rule out the front since it was sitting square on the ground.

Have you tried using a mechanics stethoscope to pin point the noise?


It did help localize the area on mine.
Good stuff,1lowcab,you pretty much covered everything.Only things I would try--pull transfer case fuse,make sure it disconnects the front differential.If it does,go drive it that way.If it makes any difference at all,drain and refill t/case with proper fluid,and drive for a while with the fuse out.Then install fuse and see.
 

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Discussion Starter · #18 ·
I drove it all summer with the front driveline out, and it was the same. I just stuck that back in the other day because the guy that built my differential said to stick it back in and try it. I tried a stethoscope and didn't have any luck tracking it down because I could hear the same thing everywhere I checked.
 

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Well then,either torque convertor,exhaust droning,or stretched transfer case chain.Dealers and better repair shops have very good vibration analyzers,they could pin it down.
 

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I tried a stethoscope and didn't have any luck tracking it down because I could hear the same thing everywhere I checked.
Exactly like mine. I could touch the engine with the stethoscope and hear it, I could touch the rearend and hear it, I could touch a body panel and hear it, lol.

Try it on jack stands with the front shaft out.

Even with the front drive shaft out when driving you can't really rule out the front as everything is still turning, making a possible source of vibration.

With just the rear up on stands you can totally rule out the front....everything in the front.

I'm telling you, I even went as far as trying 3 t-cases and rebuilding 2 of them thinking the vibration had to be coming from there. I swapped out the trans, torque converter and flex plate, it was NONE of them.

I still say its an engine firing harmonic like the service bulletin says. If I were in your shoes, knowing what I know now(and been through), I'd swap the engine. It's a hard pill to swallow but it 100% cured mine.

Like I said, my next one....I'm walking away if it has ANY TYPE of vibration to it!
I will NOT go through that again. lol!
 
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