vibrating park avenue

[Guest]

My 98 park avenue has vibration at around 60 mph to about 85 mph. Iv'e alredy tried new tires, balancing, rims, alignment, checked shocks, appear OK. What's up with this car? Dealer said don't wste money on their vibration analyzer cause he's tested several that vibrate with no apparent cause. It's very annoying. Help anyone?

[Guest Albert]

You might try removing the drive shaft, and run the car up to speed (plug the rear of the tranni frist) and see it the vibration is still there, could also be one of the brake drum wheel weights that has come off, may also try removing the rear wheels and the brake drums to see if the vibration goes away..

[Guest]

Without much detail on how the vibration occurs, have you checked wheel bearings and engine mounts?

[NTX5467]

Considering the '98 Park Avenue is a front wheel drive car, removing the driveshaft is not an option.<P>Have you had a "road force variation" procedure run on the tire/wheel assemblies? This is different than just a balance job on an electronic balancer as it requires a high end balancer that will run the wheel/tire assembly against a roller to measure the variation in stiffness in the tire as it rolls. Kind of like what we used to call "hard spots" in tires which otherwise balanced perfectly.<P>GM has published specs (in pounds of force) for car and truck tires. We have changed lots of new vehicle tires under the factory GM warranty--even the highly regarded Michelins--for the road force variation being greater than the GM spec. <P>We also has a run of Escalades which had tires which moved on the chrome rims. They would balance good with "in spec" road force variation, yet within 10 miles on smooth interstate driving, the marks on the tire/rim would move several inches apart and the tire vibration would return. In this case, putting on the Michelins cured that as they popped on much more positive than the Goodyears did.<P>Part of the road force variation procedure, is a tire rim runout check. If done properly on the GM-specified machine, the road force variation check and balance should take care of any tire/wheel vibration issue. Don't expect a tire dealer to have this machine as it could point up just how "bad" his products might be, yet GM has basically told all dealers to have this high end balance machine since GM covers all tires under the basic vehicle warranty now.<P>I concur that more information is needed. It looks like most bases have been covered, but more information is needed. Engine/trans mounts typically don't cause higher speed vehicle vibrations, but clunks when engine power levels change. Weak shocks/struts can point up tire imbalance easier than stiffer ones might, but stiffer ones would show up the road force variation quicker--still not usually a contributor to tire vibration issues on new tires, maybe after they've continually bounced for many miles and are no longer perfectly round but not with new tires, typically. Alignment is not usually a contributor to tire vibration either, especially with new tires.<P>If this issue started with new tires and the tire dealer is not admitting to anything, I strongly recommend you take the car to a GM dealer with the electronic wheel balancer that has the capabilities to check for road force variation. Explain what the deal is and see what happens. Having the road force variation balance job done according to GM standards should isolate any tire related issues--period.<P>Just some thoughts . . .<BR>NTX5467

[GSMAG]

I found a leftover '98 Park here in AZ in October of '98. I convinced my parents to buy here rather than Omaha. Deals are far better here. They took the car for a test drive before buying and found the same problem. After replacing drive axles and other front end stuff to this brand new car, the dealer received word to put on new Michelins (the tires on it were Goodyear.) The car quit vibrating. I believe there is some sort of fundamental flaw in the design of the car if it's that sensitive to different quality tires, but the new tires made it right. 40,000 miles later, it rolls on smoothly.

[our51super]

I fully agree with NTX5467 on the road force balancing. Teresa and I had a 1995 Oldsmobile Aurora with brand new Michelins on it and it vibrated much in the same manner that you describe - basically at higher speeds. I had all four tires/wheels road forced and they 'indexed' the tires to the rim and boy what a difference. I had the car close to 100 MPH and the steering wheel was rock solid. I want to say it cost us about $100 to $150 to have the road force balance job done but from now on when we get a funny vibration in the steering wheel I have that done first. I can't say enough about it.<P>Good luck!

[our51super]

fish,<P>You might want to check this site out:<BR> <A HREF="http://www.hunter.com/pub/product/product.htm" TARGET=_blank>http://www.hunter.com/pub/product/product.htm</A> <P>It shows the Hunter equipment that is used to road force tires/wheels. It might also be helpful in finding a shop that has one of these. I would suggest trying a dealership or a larger tire store since they can afford this costly piece of equipment.<P>Your other option is to wait 'till tomorrow, when Teresa and I will be announced as the grand prize winners of the 325 million dollar Big Game lottery and I will buy one of these machines and you can use it at no cost to you. <P>Cheers!

[NTX5467]

I suspect that one reason the road force variation issue has come about is that almost all cars now have 4 wheel independent suspension and have lighter weight wheels and other things in the suspensions. In prior times, there was a heavy rear axle assembly in the back that is where the tires which didn't balance out well or took more weight were typically put. The additional weight of the rear axle made it harder for the wheel balance/road force variation to generate vibrations and such which would be felt in the car. Plus, the cars now are at least 500 pounds lighter than they were back then too. These are basic design features of modern vehicles. <P>The GM specs for road force variation are greater for the light truck vehicles than they are for the cars.<P>In the past, there were other strategies to make the tires more round and smooth running. In the 1960s and 1970s, it was Tire Truing (where the tire tread was ground off to make it completely round). The later '70s saw "Match Mounting" where the dot on the sidewall was matched to the valve stem hole (the dot representing the "high spot" on the tire and the valve stem hole being the "low spot" on the wheel--as we were told back then). That has evolved into the Road Force Variation mounting and balancing procedure of the current times.<P>Enjoy!<BR>NTX5467

[Guest DougLen]

I own and love a 2002 PA Ultra. When I bought it, it needed everything. So, system by system, I have been going through it. I replaced the whole front suspension including struts, tires, control arms, tie rod ends, power steering axle, etc., and was surprised that it still had the vibration you all are describing. No question, it needed all those things anyway, so I didn't waste my money. But it didn't address the vibration between 68 and 75mph. Then I thought back to the old rear wheel drive days and what would cause the vibration in my old muscle car. I decided to check both the CV joint (the front wheel function of a differential) and the motor mounts. The CV was fine, but the front motor mount (actually called the transmission mount at most parts places) was totally shot. I replaced it and most of the vibration went away. I still have a small vibration at 70mph, so I'm going to replace the three rear motor mounts. But the front tranny mount is the main culprit for this kind of vibration in many high mileage PA's. Doug

[60FlatTop]

Put one of the rear windows down about 3". You'll never notice the vibration again.

Bernie

[cg22]

I had similar issue on my 02 Park Ave. , but only at 45-50mph. I first changed out mount near radiator, this helped some, then changed out mount near right front tire. Problem solved.  Thank you guys for you wisdom and time, you saved me lots of hours and running around chasing my tail.