2002 astro vibration/shudder problem

Hi, I have a 2002 Astro that has developed a "shudder" problem mainly at speeds above 65 mph. The sudder isn't real bad but it can be felt in the seat and floor but the steering wheel remains steady for the most part. I have had the van to 3 different mechanics and had the service manager at the chev. dealership (friend of mine) try to diagnose the problem but no one seems to know what is causing the shudder. I have replaced the trans mount, U-joints, had the transmission checked and serviced, and new tires all around but the problem is still there, however doing these things seems to have made some improvment.
Any ideas of what the problem may be would be appreciated.

RWD or AWD Astro? A transfer case on an AWD could be a problem.

Thanks for your reply, this is a 2 WD Astro.
This is the 4th Astro van I have owned in 18 years and this is the first time I've had a problem like this, and it came on suddenly.
I can't remember doing anything or haveing anything done to the van before this started.

Have you ever had out of balance wheels? Does it feel like that?

Jonsonton,
It's not out of balance wheels, I have had new tires put on, rotated them twice but no difference. I don't feel vibration in the steering wheel, it's more like a shudder in the seat and floorl

Thanks for the post.

While at speed, no cruise control... and when the shudder occurs.... touch the brakes. Does the shudder stop?

CD Smalley,
The sudder starts to be more noticable when I reach 65 mph or above, it does not stop when I touch the brakes, it's still there when I use cruise control, the strange this about this is that it's been doing this since June 2006 and has not gotten any worse, in fact it's improved since I then. It's improved the most since I had the trans. serviced. The trans shop swears it's not the lock up torque converter or the converter clutch, but from everything I've heard, my opinion is that it is in the tranny somewhere.
My neighbor builds transmissions for a living, has been for over 15 years, he doesn't think it's the transmission either, but I'm still not sure. I don't want to just start pouring money into it in a trial and error mode, especially since I have driven it for thousands of miles and it's not gotten any worse or has not thrown a code for the check engine light to come on.

Thanks

I wonder if you have the driveshaft in out of phase???

Anytime you remove the driveshaft you must re-install it in the same position. If you put it in 180* from where it was, it will vibrate like that sometimes.

Someting cheap to try.

At 65+ MPH, what happens if you back off the fuel and move the trans into neutral?

CD,
How would I know if the drive shaft was put in it's original position?
Also, I purchased this van new and when this problem started the drive shaft had never been removed from it's factory position, it has only been removed once when I put new U-Joints in it.
An out of balance drive shaft had been suggested and I have never had it checked for balance, but there is no evidence that there is a weight missing.

Any other ideas?




I wonder if you have the driveshaft in out of phase???

Anytime you remove the driveshaft you must re-install it in the same position. If you put it in 180* from where it was, it will vibrate like that sometimes.

Someting cheap to try.

Bowtie,
It seems like we tried this once and the shudder did not go away but I will try it again and see what happens.
If the shudder stops it would seem that it could be in the drive train but if it is still there it would not make sense to me that it would be in the drive train, rather somewhere in the wheels or front end.
However, all of the mechanics that drove the van seem to think it is coming mostly from the rear of the van.
It's really hard to tell where it's coming from, but like I have said, it seems to have improved since I had the trans serviced leaving me to think it could be in the tranny. My neighbor who builds transmissions for a living put his scanner on it and everything showed normal. He does not think it is in the transmission. I'm not sure he is right but I really don't want to start putting a lot of money into the transmission on the chance it might be. After every other possibility has been eliminated I may not have a choice but to try that.

Thanks




At 65+ MPH, what happens if you back off the fuel and move the trans into neutral?

As far as knowing by looking, most likely you can't. If I remove one I always scratch the driveshaft and the differential with an awl or mark them with a Sharpie so I know where to put them back.

I had a similar problem on my 9C1. I took the driveshaft out and had new u-joint installed and had it balanced. That fixed it for me.

Aren't there counter weights attached to the rear drums? Oh wait, does your van have rear discs or drums?

Should be rear drums.

If all else fails, it may be time to strap in a transducer and frequency counter, or at least a harmonic reed tachometer to indicate the range of vibration frequencies. That can help determine if the problem is in the wheel/axle or driveshaft/transmission.

At 65+ MPH when I take my foot off the gas and put the transmission in neutral the shudder does not go away.
I'm beginning to feel it at lower speeds also although not nearly as bad.
Could it be something in the front end?
Could it be bearings? Front or rear?

If the vibration feels like it is happening 12-15 times per second, it is likely due to wheels, tires, or something related to axles. If the vibration feels like it is happening 60 or more times per second (more of a "buzz" than a "shake") it is more likely related to the transmission, driveshaft, or torque converter. It may be difficult to determine this just by seat-of-the-pants feel.

Another thing you can do to eliminate the torque converter is to run the vehicle in DRIVE instead of OD. If the vibrations occur at the same speed ranges, it is not likely a torque converter or transmission issue.

Verify that the front wheel bearings are packed and preloaded correctly. Check the rear wheel bearings for radial and axial play (there are side gear shims and a few thicknesses of "C" clips available to adjust axial play).

Inspect the tire carcasses closely for sidewall or tread bulges (I'm seeing this a lot more in new tires, and it is supposedly "normal") or signs of tread squirm.

If you can raise and securely support the vehicle and reach the same indicated speed, you may be able to determine if the tires themselves are at fault.

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Join Date: Oct 2004
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Re: 99 vibration ?
Check out this story. I hope it helps Aloha, John4.I changed the left rear axle bearing and it cured the problem.The bearing did not show excessive wear and there was no play in the axle. The bearing did show signs of excess heat. It appears that the bearing got tighter has it warmed up. Hope this can help someone with a similar problem.

I have similar problems with a 2001 Astro 2 wheel drive. Have replaced shocks and had multiple attempts to get tires balanced. The vibration seems to be from the rear tires and is present between 65 and 75 MPH. Shifting into Netural and varying the engine rpm has no effect on the vibration. Also, no change if driving with or without overdrive. Vibration seems to get worse when transitioning from level coast to slight acceleration. After rounding long slow curves the vibration will change slightly as the tires change to a differeng rotation relationship with each other. Seems like when an imbalance of both rear tires are in synk with each other, the hop gets worse. The tire hop is severe enough to cause vibration throughout the van and does not seem to be from the front end at all.

Just returned from Florida where the roads were very smooth and the vibration was very noticable. My tires are Uniroyal Tiger Paws with less than 40% wear. The tires do not show any delamination or brusing problems and have been rotated and balanced every 5 to 6 thousand miles. They were rotated and balanced just before leaving on vacation to Florida.

The tire hop is enough to make the vehicle seem a bit unstable around 70 mph. I am heading back to the tire dealership tomorrow morning since I just returned from my Florida trip. This is my 3rd Astro and I did not have this problem on the earlier 94 and 96 Astro's. I have 70,000 miles on my 2001 Astro.

I did replace the front rotors and the bearings were repacked as well as new brake pads installed. No change to vibration.

I have noticed that the tire dealerships all seem to be using a very slow rpm balancing machine.

I will be interested in your findings and will post any findings on my similar problem as events change.

It could be engine. Try driving in each gear, run up the rpm. Uphill under power or downhill, coasting may give a clue if it's tranny or driveline. My initial suspicion though is an out-of-round tire if it's strictly high speed related.

give a thought to wheel bearings also.
cleaning and repacking the fronts is a cheap
try.
prehaps the rear bearings ?
something to think about

It could be engine. Try driving in each gear, run up the rpm. Uphill under power or downhill, coasting may give a clue if it's tranny or driveline. My initial suspicion though is an out-of-round tire if it's strictly high speed related.

He's already tried coasting in neutral at 65 MPH with no reduction in the vibration.

One mechanic I talked to seems to think it might be rear bearings, he said if it were anything in the front end I would feel it in the steering wheel rather than in the seat.
He said to leave it with him and let him look it over more carefully to see if he can figure out what it is.
I guess at this point I don't have much choice but to do that.

Thanks for all your help, I'll post the problem and the fix if / when I find out what it is.

One mechanic I talked to seems to think it might be rear bearings, he said if it were anything in the front end I would feel it in the steering wheel rather than in the seat.
He said to leave it with him and let him look it over more carefully to see if he can figure out what it is.
I guess at this point I don't have much choice but to do that.

Thanks for all your help, I'll post the problem and the fix if / when I find out what it is.
That is exactly where I am now in working with AutoTire on resolving the problem. The only thing I can add about my 2001 is that the tire hop got worse after the last balance and rotation which makes me think the problem tire was on the front before and did not create as much of a problem there. So, it may be a combination of tire and rear bearing issue. Stay tuned...

Just got back from AutoTire and my problem is resolved. Turns out that both rear tires were only slightly out-of-round and the max out of balance was only 1/2 oz. This explains why my problem would come and go as the out-of-round conditions would only cause the severe vibration/hop when each tire was in a rotation alignment that resulted in the problem. AutoTire agreed to replace the two tires at 1/2 price. The new tires were balanced and we verified nearly no out-of-round condition. The van is now very smooth all the way up to 75 which is the fastest it was driven during a test drive.

2002 astro vibration/shudder problem - When driving with the cruise control set at 70 mph the vribration/shudder is not constant all the time, it seems to come and go and various intervals.

Any new ideas as to what might be causing this problem would be appreciated.

2002 astro vibration/shudder problem - When driving with the cruise control set at 70 mph the vribration/shudder is not constant all the time, it seems to come and go and various intervals.

Any new ideas as to what might be causing this problem would be appreciated.

That was exactly how my 2001 acted. I found that as I would round a long curve causing the back tires to change rotational relationship with each other, the vibration/shudder would come and go. I think the natural vibration frequency of the rear suspension on these astros can be excited by a simple out-of-round tire. Mine was not that much out-of-round but caused the rear suspension to go into a shudder response at 65-75 mph. I wish you were in the st. louis area and could try my new tires/wheels on your astro to see if that solved your problem. I now am running with no shudder at all. I had the problem for about 2 years and what a difference now.

Inspect the tire carcasses closely for sidewall or tread bulges (I'm seeing this a lot more in new tires, and it is supposedly "normal") or signs of tread squirm.

If you can raise and securely support the vehicle and reach the same indicated speed, you may be able to determine if the tires themselves are at fault.

Just got back from AutoTire and my problem is resolved. Turns out that both rear tires were only slightly out-of-round and the max out of balance was only 1/2 oz.

That's what I've been seeing a lot more in the last 4-6 years. It seems that tire quality control has really been suffering unless you go with premium tires. The one-ply sidewalls really scare me, too. Check your tire markings - There are a lot more of those being made.

my 88 astro with a 700 r 4 started doing this.and i was telling a buddy that rebuilds them about a shudder and he hooked me up with something called shutter Doctor it seams when you replace the fluid you lose the additives in the tork converter that are in it when its new and this puts it back.i put in the tube and 2 days later it stopped. it's worth a try. and that is my.:2cents: worth

Where do I find Shudder Doctor captinhowdy, and hey saturnguy2,
I have had 3 Astro/Safari vans and they all have done the same thing. At 65mph they started vibrating exactly as you and others have described. On my first 1995 van, I had everything checked out; driving in 3rd gear instead of overdrive, neutral coasting, balanced tires, checked for out-of-round, alignments, new set of wheels (twice), shocks, bearings, new(rebuilt) transmission, changed driveshaft....nothing seemed to fix it. Like my 1985 Safari, my 1992 Astro did it too (i junked them both, took'em across the scales) and now my 2005 Safari has started doing it at 80,000 miles. One thing I noticed about the 2005's and newer is they don't have nearly the tight turning radius of the older models. GM put 16" wheels on them starting in '05, instead of the 15" wheels they used to use on the previous years. I'm really displeased about the larger turning radius but thought GM might have done this as a trade-off to eliminate the shaky vibration problem of the '95-'04 models at 65mph and above. Obviously that was just wishful thinking on my part. The only way I knew to find out for certain was to buy one and hope for the best. So much for hope. You'd think I'd have learned not to buy these problems. The 4.3L,V-6, is a workhorse that pulls well and gets good gas mileage, although they do start smoking after about 200,000 miles even if you are religious about changing the oil and filter every 3,000 miles (I did and still do). I'm going to take it in to the dealership and see what they can figure out. My 2005 Safari is from a different dealership than my others and maybe they are more savvy. Let's hope. If not, I'm going to trade it in on something else. If you ever do get a fix, please post it. I still think from all I've done and read about this common problemis that it is probably the front ball joints/tie rods or a matter of replacing the entire front end. Ouch, on the whole thing.
Again, keep posting developments, I'll post what I learn, if anything.

This is the 4th astro van that I've owned and the only one that I've had this problem with.
The local garage told me that one of my tires had excessive runout and needed to be replaced. He said that was what was causing the vibration.
I have not replace the tire yet but I probably will, I have nothing to lose.
If this does not solve the problem I will trade it in on a pickup.
GM made the right move when they discontinued the Astro van, it's not often that GM does anything right.

Thanks for the post.







Where do I find Shudder Doctor captinhowdy, and hey saturnguy2,
I have had 3 Astro/Safari vans and they all have done the same thing. At 65mph they started vibrating exactly as you and others have described. On my first 1995 van, I had everything checked out; driving in 3rd gear instead of overdrive, neutral coasting, balanced tires, checked for out-of-round, alignments, new set of wheels (twice), shocks, bearings, new(rebuilt) transmission, changed driveshaft....nothing seemed to fix it. Like my 1985 Safari, my 1992 Astro did it too (i junked them both, took'em across the scales) and now my 2005 Safari has started doing it at 80,000 miles. One thing I noticed about the 2005's and newer is they don't have nearly the tight turning radius of the older models. GM put 16" wheels on them starting in '05, instead of the 15" wheels they used to use on the previous years. I'm really displeased about the larger turning radius but thought GM might have done this as a trade-off to eliminate the shaky vibration problem of the '95-'04 models at 65mph and above. Obviously that was just wishful thinking on my part. The only way I knew to find out for certain was to buy one and hope for the best. So much for hope. You'd think I'd have learned not to buy these problems. The 4.3L,V-6, is a workhorse that pulls well and gets good gas mileage, although they do start smoking after about 200,000 miles even if you are religious about changing the oil and filter every 3,000 miles (I did and still do). I'm going to take it in to the dealership and see what they can figure out. My 2005 Safari is from a different dealership than my others and maybe they are more savvy. Let's hope. If not, I'm going to trade it in on something else. If you ever do get a fix, please post it. I still think from all I've done and read about this common problemis that it is probably the front ball joints/tie rods or a matter of replacing the entire front end. Ouch, on the whole thing.
Again, keep posting developments, I'll post what I learn, if anything.

Perhaps a bent or dented drive shaft?? Hit any debris on the road lately??

I finally solved the problem of the vibration in my 02 astro van.
It turned out to be an out of round tire. The way I found out was to have it balanced on a machine that checks road force and also checks for out of round conditions of the wheel and tire. Most shops do not use this type of balancer.
Anyway, once the problem was found, I had the tire replaced and it cured the vibration.
From now on I will have my tires balanced on a top of the line machine.

Bravo

mine is a 99 chevy astro rwd. it only shakes when i'm stopped, but if i shift it into neutral it stops. I've already tried replacing the brakes, rotors, bearings, u joints, serviced the transm, serviced the read diff, and replaced the tss. All with no improvement. any suggestions anyone?

and i almost forgot i have also replaced all 4 tires, the inner and outer tie rod ends, sway bar bushings and linkages, had all the new tires balanced and aligned and still no diff in the vibration.

My '94 Safari has a similar problem, The vibration is worst at 110KMH. All the wheels have new rubber and have been balanced. I took the driveshaft (there was a smooth spot on the shaft that suggested a thrown weight) to a balancing shop and it did nothing to alleviate the problem. I have to think that it was not balanced at that shop. I'm considering going to a wrecker to get another driveshaft.

Does anyone know how to calculate the driveshaft's rpm at any given road speed?

This is a reply to Hegedus: Maybe motor mount(s)?