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98 STS: Vibration at or around 60-70 MPH


AKolodny

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Dear Colleagues,

My 1998 Seville STS with around 71K miles will begin vibrating at around 60-70 MPH. If I accelerate past that speed range, the vibration will die down, and if I remain under 55, I don't experience that vibration. I can feal it in the gas pedal, and I look over and see the passenger seat head rest vibrating. Also, it seems to be worse with the AC running vs. the windows down. Does anyone have suggestions as to the problem?

Most Gratefully,

Alan

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Welcome to Caddyinfo.

Probably worn inner or outer CV joints on one side. Easiest is to replace the half-axle on one side or the other as needed. The assembly costs around $200-250 as I recall plus installation. Check gmotors.com or gmpartsdirect.com once you get to that.

To check though, put the car up and see if you have any play in the suspension, or the wheels. Then look for a torn boot along the axle CV joints.

Bruce

2016 Cadillac ATS-V gray/black

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Sounds like the car needs a road force tire balance. Check with your local Cadillac dealer and see if they are equipped to do it.

Charles

Yes, common problem, Hunter Road Force Balance is the cure.

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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Sounds like the car needs a road force tire balance. Check with your local Cadillac dealer and see if they are equipped to do it.

Charles

Yes, common problem, Hunter Road Force Balance is the cure.

I concur

2001 STS Mettalic Otter Grey, Black Leather, 213,000 kilometers - miles - ? Still running strong!

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I have had the same type of vibration with a 1993 STS and 1998 STS I used to own. In both cars, the crappy Goodyear(Goodferayear) Eagle GA tires were the culprit. I replaced them with something better and the vibration went away.

K.O.T.

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I have had the same type of vibration with a 1993 STS and 1998 STS I used to own. In both cars, the crappy Goodyear(Goodferayear) Eagle GA tires were the culprit. I replaced them with something better and the vibration went away.

I had a 94 Concours with about the same mileage on it..was having the same vibration problem, but at around 50-55. I couldn't figure it out, 3 mechanics couldn't figure it out...Balanced tires, changed CV axles, nearly sold the car because of it. We finally bit the bullet and went to the "stealership" (saw that word here tonight and liked it) and they determined it was carbon buildup in the EGR, but not enough to send a code to the service engine light. Once they cleaned that out, she did great for another 30K miles. This might not be your problem but thought I would share.

"Torque it down 'til it strips. Then back off half a turn."

www.picturetrail.com/carolinagreg

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I have had the same type of vibration with a 1993 STS and 1998 STS I used to own. In both cars, the crappy Goodyear(Goodferayear) Eagle GA tires were the culprit. I replaced them with something better and the vibration went away.

the "stealership" (saw that word here tonight and liked it)

Yeah - I love that term too.... it is so fitting.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Please let us know how this gets resolved.

By a strange coincidence, my '99 STS has developed a bad front end vibration, like an unbalanced wheel, in the 60mph to 70mph range. Seems to come from the left (drivers) side. But the wheel weights are all in place so I'm thinking it must be something else - something more expensive :(

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Do a search for "Ruby's Viberator" and "Ruby's Viberator, The Final Chapter" for my tale of woe on viberation. BTW, she is still viberation free today.

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Do a search for "Ruby's Viberator" and "Ruby's Viberator, The Final Chapter" for my tale of woe on viberation. BTW, she is still viberation free today.

That, and other threads linked to from within those threads, are a very long read.

What I got from it was:

1) a road force wheel balance (which might indicate you need new tires) sometimes works, but didn't do anything for some.

2) the front cradle can get sloppy - you can replace the rubber bushings, it might help. No permanent fix available.

3) adding the GM strut brace might help a little, but isn't a cure.

4) other - e.g. hubs are worn and there is too much free play.

It appears the 60-70mph wheel bounce problem does not have only one cause, can be a combination of several problems, and the solution is going to require some trial and error - and expense.

I'll check the rubber bushings this weekend and call around for quotes on the road force balancing. Here is a link to find out where in the US you can get it done:

GSP9700

Here is the strut brace at gmpartsdirect. 'bout $30 with shipping:

part # 25653157

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.... Does anyone have suggestions as to the problem?

Most Gratefully,

Alan

The Service Manual for the '98 Seville includes a 33 page section on "Vibration Diagnosis and Correction". You can avoid spending money on parts / labor by indentifying the source of the vibration.

Tires are the favored target because they can be out of round, out of balance, break belts and other unpleasant things that you can't see. If you choose to try the balance route first, ask the machine operator to be alert for signs of a bent wheel.

But before you do that, there are some simple but labor intensive steps you can do in your driveway to eliminate some of the nuisance causes of vibration that might not require replacing any parts. Remove the wheels and inspect carefully for signs of damage like a bent flange or evidence that a weight has been thrown off. Use a wire brush to scrub any rust or corrosion from the surface of the rotor where the wheel mounts. Thoroughly clean the wheel paying attention to the inboard surface. More wire brush on the wheel to rotor mounting surface. Put the wheels back on using the correct tightening sequence and proper torque value (100 lb ft.)

Also try a different engine speed when you get the vibration; simply pull the gear selector down to "3" or "2" and note any difference in vibration level.

Good luck with identifying the "source". It can be tedious and frustrating.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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I haven't seen anyone mention this:

I've had hard to balance wheels on a few cars in the past, and it took an oldtimer to show and fix the problem after many tries at balancing.

He showed me that most of the balancers mount with a cone to the center hole. Problem with a lot of wheels, the center hole is not accurate enough.

You need to ask/tell the tire shop to use the LUG MOUNT ADAPTER. They don't care to use it because it has to be mounted on each wheel separately. Not like the cone where they just slap the wheel on the balancer.

You can often see way too many weights on the wheel that bounces at 60.

I even had a tire mounter at Costco tell me two wheels were bent. Then while driving down the road, it was bouncing.

This jarred my memory and I went back to Costco and asked the mgr if they had a lug mounting adapter. He dug it out and after testing the supposed balanced wheel to see it was not balanced, he used the lug mount and it took very little weights. So he redid all four and said he learned something new. Oh and the wheels were not bent!

Bob B

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Thanks for the extra advice. My wheel hop built up over a short time and is now impossible to live with. Starts at 60mph, gone by 70mph.

Imagine a wheel that's way out of balance, that's how my car is - but no wheel weights are missing. I'll do the easy thing first and rotate the wheels front to rear and left to right. The rears used to be on the front and are getting very near to needing replacement. If the rotate doesn't help, I may just use the occasion to get two new front tires anyway and go from there.

Strangely, using the GSP9700 search engine to find a road force machine, none of the local tire shops have one. Only car dealers have them around here, and one Firestone shop.

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Thanks for the extra advice. My wheel hop built up over a short time and is now impossible to live with. Starts at 60mph, gone by 70mph.

Imagine a wheel that's way out of balance, that's how my car is - but no wheel weights are missing. I'll do the easy thing first and rotate the wheels front to rear and left to right. The rears used to be on the front and are getting very near to needing replacement. If the rotate doesn't help, I may just use the occasion to get two new front tires anyway and go from there.

Strangely, using the GSP9700 search engine to find a road force machine, none of the local tire shops have one. Only car dealers have them around here, and one Firestone shop.

--------------------------------------------------------------------------------------------

BTW, Mine were bouncing only in a range around the 60 mph. Had it happen on two different cars. When you speed up or slow down it went away.

Can anybody explain road force balance?

And does it by chance use the lugs to mount? Or is it the old method of balancing on the car? Spin balance while mounted by the Lugs??

Bob B

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Thanks for the extra advice. My wheel hop built up over a short time and is now impossible to live with. Starts at 60mph, gone by 70mph.

Imagine a wheel that's way out of balance, that's how my car is - but no wheel weights are missing. I'll do the easy thing first and rotate the wheels front to rear and left to right. The rears used to be on the front and are getting very near to needing replacement. If the rotate doesn't help, I may just use the occasion to get two new front tires anyway and go from there.

Strangely, using the GSP9700 search engine to find a road force machine, none of the local tire shops have one. Only car dealers have them around here, and one Firestone shop.

There are lots of shops with the GSP9700 that aren't on that web site. The shop that I used for example was not on that site... Before you give up... open up the yellow pages and make some calls.

And regarding RFB sometimes not working... Like all balancing... the result really depends on the quality of the tires and wheels going in... RFB measures the wheel for any high an low spots and them measures the tire for a soft or hard spot and then the system tries to match the tires soft spot with the wheels high spot... (did that make sense)...

Herein lies the problem, If your tire is a POS (like some of the RSAs, nuff said) and has 2 or three soft spots RFB will only help but won't cure your issue.

But the Balancer will know and should tell you this... Any tire wheel combo that has a RFB rating of over 12 pounds will be noticed on these cars. You really need to take the time to watch the process. It is cool. The machine will pass a tire/wheel with up to 15 pounds but you are going to feel tire at that level.

And the only way to solve this is to buy a quality (expensive) set of tires...

Micheline A/S Pilots with RFB numbers in the single digits solved my vibration.

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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Not even an honerable mention.....boy am I dissapointed.

Anyway, if you haven't changed tires in the recent past, I'd suspect that you may have a belt or tread seperation problem. A common failure of tires that have been in service for a long time, and potentially very dangerous. Nothing will "cure" a tire that has internal damage...you just have to replace it. Conventional spin balancing will not reveal the damage, nor will static balance. New rubber bushings and strut braces will only mask the problem for a while. The only diagnosis is to do a road force balance as others have mentioned (in a different light though). Look for a tire that has outlived its useful life, then change all that are of the same age.

Now if the wife, son or you have hit something and bent a wheel, that is another matter enTIREly.

Never underestimate the amount of a persons greed.

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When I first bought my caddy, I had the same vibration. Two Balancings did not help. Bought a set of Michelin X radials and the vibration was gone. Attributed the problem to old crappy tires.

What's a Hunter RFB typically run?

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This is a problem that has to tackled in a very organized manner. You must eliminate one problem at a time. If the vibration goes away at higher speeds, something must center or balance itself as the speed increases. I am surprised that no one has focused in on Bruce's suggestion more, an axle would come back into center or balance at a higher speed.

I would make a checklist that backs down as follows:

Check tires (balance, roundness, pressure, etc). Any odd wear on your tires? Raised tread, choppy, roughness, inside or outside wear, center wear, cupping, repeat pattern?

Rotate and balance your tires and see if the problem changes. Front to back.

Jack car up and check at 9 and 3 and 12 and 6 o'clock for looseness, any looseness should be eliminated by replacing worn parts

Does the vibration radiate through the steering wheel or do you feel it in your seat? If you feel it in your steering wheel look at balance, tie rod, hub bearing problems, if you feel it in your seat look at strut assembly, out of round tire, engine mount, ball joint problems. Not in any particular order. From your description it seems you are feeling it in the body.

Pull the front wheels and clean the hub flange, and wheel of all rust, sediment, etc

Re-torque the wheels to 100 ft. lbs. after checking the bolt holes and wheel bolts for worn tapers.

Inspect the axles for it throwing grease, grab and feel for looseness, do a series of circles in a parking lot slowly and listen for clicking, do that in both directions.

Lift the hood, put the car in drive put foot firmly on brake, raise RPM to 1000 easily and look for unusual engine movement indicating a bad engine mount, do the same in reverse. This is easier if you can get a helper who you trust to do this while you look under the hood yourself. Keep your body clear of engine at all times. Visually inspect the engine mounts for cracking or damage or in some cases leaking of fluid. That this vibration changes with the AC on, makes me think that its related to the engine mounts.

See if this problem stops/changes if you take the selector out of OD and put it into D and 2. Its sounding to me like the increased torque due to the AC drag is creating a harmonic, changing the selector would indicate its drivetrain related, again indicating engine mount or engine movement.

Remove your serpentine belt and grab your AC pulley hub and see if you have any looseness in the hub bearing. With the AC on, the hub might be binding and putting a strain on the engine causing a sort of vibration, I would think however that the hub would overheat if that was happening. Look for overheating at the hub. It is also possible that the AC strain changes the harmonic of the problem making it more obvious, again making me think its engine mount related. Check the dog bones also for looseness if you have them.

Have someone drive your car, follow it and look for dog tracking, have them drive in the range that it vibrates and circle the car, looking at the front wheels for bouncing, that could indicate an out of round tire or a bad strut or both.

Have your alignment checked

Report back any findings with some of the tests I suggested

Pre-1995 - DTC codes OBD1  >>

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  • 2 weeks later...

Update - rotated front wheels to opposite rear. Still a nasty front unbalance, but with wider mph range and less violence. Bumpy from 50mph to 70mph. The rears have no problem. Wheels which bounce on the front are smooth on the rear.

The fronts were getting close to the wear indicators and the sidewalls had a few splits so I got new tires - Goodyear Assurance Comfortred. Road Force Balanced to less than 15 (of whatever the units are), and the front still has a bounce and it's less than before, but still bad enough to be unacceptable in a Cadillac. Maybe it's fine for an old Yugo that's bounced a few curbs.

I'll have to put in more effort to improve the situation. Probably a front Road Force Balance of ZERO would give a perfect ride, but that's not realistic. I'm leaning towards a loose cradle as the root of the problem. When the mounts are worn, it just doesn't resist and attenuate the front vibrations which will occur with all real world non perfect wheels and tires. At one time the car rode smooth, so something changed and I think it's the cradle mounts.

Don't expect any more updates for a while, this isn't going to be a quick fix :(

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What were your road force numbers. If the shop is doing this right they will give you a report that tells you:

1) the run-out of each wheel

2) the road force number before

3) the road force number after...

The machine will pass anything less than 15 but as I have said before on our cars anything over 11 is a fail... and try for low single digits on the front pair.

BTW you need to get all four done one bad wheel will ruin your whole day and it is not always easy to tell which corner is causing the problem

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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I just went through the exact same problem and it was the drivers side half shaft.

Big Jay

Life is too short to grow up!

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