Hello, I have a 1969 Buick Wildcat with a 1970 buick 455 engine. I've been having some trouble with dashboard flutter on the highway, and I was wondering if you guys have any ideas? I made sure my tires were inflated to the proper pressure, and my wheels have been balanced. The flutter is periodic (every few seconds on certain spans of the freeway) so it makes me think it's not something in the drivetrain. I have OEM specification shocks in the front and adjustable air shocks in the rear that I keep at about 40 psi. The rear seems to sit a little high, while the 1969 Wildcats (when new) in the car catalogs seem to have the opposite bias. I was wondering if maybe having shocks of different hardness is causing my car to have some sort of resonance when I'm on the freeway? It seems to get worse when I have more people in the car or when I have low tire pressure. Currently I run the stock 15 inch wheels with the 225 75/R15 firestone radials. I notice when I pump up my rear shocks to about 100 psi it gets worse. Do you guys think my car's angle of attack might have something to do with it too? This picture was taken before I changed the wheels to stock. The car is exceptionally smooth on surface roads. What sort of shock setups do you guys run? What sort of brands do you guys recommend? The dashboard doesn't seem loose, although it isn't as tight as my Corvair's. My plan was to go with medium-hard hydraulic shocks all around so I could still take the mountain roads but also maintain a smooth ride on the highway while hopefully eliminating that annoying dashboard flutter.
The U-joint that connects the transmission to the driveshaft? I installed the transmission a few months ago and it seemed fine. Would there be any visual signs of the U-joint going bad?
Rusted out below the windshield area in the upper cowl area, a common problem with some older Buicks ?? o No:
The car did spend some time in the Bay Area, but it's pretty rust free and I never notice any water leaking in during the rainy season (and I've driven my car in some pretty heavy rains), which it would if the cowl were rusted through and thus causing the dash the vibrate right? Also the car is very stable (more or less vibration free) after 90 mph up to 120+ (I haven't gone any faster, that was already exceeding my tire ratings by 7 mph), if the u-joint was worn out wouldn't the vibration increase porportionally with the throttle?
you need to determine if it is a car speed related vibration or engine rpm related vibration. an engine miss will give an impression of a vibration too..i had a bent rear axle on my wildcat. i had a vibration and a friend was following me and said my tire was wobbling, sure enough a bent axle..i also bought some rims off ebay and one rim had exessive run out so it was galloping..so once again figure out if its a speed or rpm related vibration.
I checked the U-joint that connects the transmission to the drive shaft, it seems tight, no play whatsoever when I push up on it or push in sides. It doesn't seem worn. I imagine there'd be some slop in a worn u-joint right? ---------- Post added at 08:51 PM ---------- Previous post was at 08:37 PM ---------- Well I put the rear on jackstands and ran the engine to about 120 mph, it seemed to be pretty smooth. I didn't notice any wobble in the rear wheels. It doesn't seem to be anything with the drivetrain. I had the rear axle checked about a year ago by a pretty competent shop and they said it was straight, and I've had the problem since before then. I also had the problem when I had the 16 inch low profile tires shown in the picture, but it improved once I went stock. I'm pretty sure it's speed related. I had my father follow me from his work and he doesn't notice anything wrong with the way the car is driving. We had the front bushings replaced and it again improved, but I still get that periodic dash vibration. ---------- Post added at 08:53 PM ---------- Previous post was at 08:51 PM ---------- I also have new sparkplugs, new engine, mallory ignition, and new sparkplug wires. The engine idles smoothly, I don't believe it's missing.
Drive shaft could also be out of balance. When you looked at the joints did you pull the drive shaft and look into each of the caps front and rear? I also am having a weird pusating vibration im trying to track down. Im thinking I threw a tire weight.
With the rear of the car that high it could very possibly be pinion angle. Let th air of of the rear shocks to 5 lbs. or so & give it a try.
No I literally just went underneath the car and pushed on the connection, I'll do that today though since I have more time. Wouldn't an unbalanced drive shaft make itself apparent when I had the rear of my car on jackstands? I did that whole test with the car in drive. Well I used to ride with the rear shocks at twenty or so (the minimum) and I still had that problem, but I'll give it a try to see how it improved things since I had my bushings replaced. Even with the rear air pressure at a minimum the car still maintains a a pretty significant angle, do you think the front sits that low because the springs are worn out, or do you think someone put extra long springs in the rear to give it that angle? I inspected the rear and I couldn't find any spacers. I was the told the second to last owner was trying to hotrod the car.
so it seems you are convinced its speed related, not rpm related so that rules out the engine..if it was my car i would be looking at the driveline, this is prob a dumb question but are the tires balanced and not separating? i highly doubt the hieght of your car is giving you a vibration. if you are concerned about the hieght it could be because the previous owner had the springs changed and the shop could have put in overload springs..i had a shop supply me with springs and they did that to me..i gave them back because the car sat too high and was too rough... The Driveshaft has a rubber damper in it, check to see if the u joint yokes are in phase..meaning the front u joint and the back u joint are perfectly in line.(phased) if they are out a little bit it could be possible that the inner tube of the driveshaft twisted in the rubber..this will give a vibration, or as someone else mentioned the driveshaft could be out of balance? Good luck...
Well, I went to the junkyard and removed some stock springs from a 1967 Wildcat, which are apparently similar to what they used in the 1969 according the the parts interchangeability book. After removing the springs from my car I figured out I indeed had overload spring installed by the previous owner, as I originally suspected. As a result of the swap that periodic dash vibration has disappeared and my car has finally been returned to stock ride height. I also switched to brand new tries which helped tremendously. It seems to handle better, feels more like a car as opposed to a truck. Thank you guys for your input though.
