I need some suggestions diagnosing a problem that has developed in my Grand National. I've been running this set-up for years and never had any stability issues before: UP FRONT: 90/10 shocks.....Loosened upper and lower control arms w/jam nuts....Stock GM Springs.....No sway bar. OUT BACK: Stock GM shocks....Stock GM springs....Airbags equal on both sides....Stock sway bar. When I'm out on a smooth straight two lane highway that has about a 2 mile area where you can let it rip......... As soon as i get up over 100-105-110 the rear of the car sets up a violent side to side rear end sway, almost as if you were whipping the steering back and forth. There is no feeling in the steering.....it is definately something out back. I tried hopping on the brakes, doesn't help. You have to get the car back down under 100 for it to stop. The first time this happened it caught me off guard and I almost lost it. I need to find out what this is because it is dangerous. Any suggestions would be greatly appreciated !!!!
HOW ABOUT THIS...KEEP IT UNDER 100 MPH OR OVER 110....LOL What are you doing going that fast anyways in New York traffic ????I am heading to Long Island this weekend and can't wait till I get there to go 100 in the Toyota!!!!Seriously,I know this may sound dumb,but have you checked the obvious like wheels tight and pressure? How about lifting the rear and seeing if there is too much play in the rear axles..Just a thought,Dustin and I were towing a GS from New York and went almost 100 miles till the loose lugnuts showed their hand. Pat
Ron It almost sounds as if you are describing an aero dynamic lift. The top profile of a car, especially fastbacks, resembles an airfoil. The faster you go the more the low pressure area over the top which is often closer to the rear. So the faster you go the lighter the rear. However we have all seen these cars run over 150 at the strip. So my question is did it ever drive OK at that speed and is this a new development? It there anything different about your car compared to other GNs? Jacked up in the rear? Missing a short spoiler?
Jim, I haven't changed a thing on this car. This is something that suddenly developed. I have only used the car three times in the last 6 months. Now that I think about it, I had a new Posi unit installed by my shop back then, after that is when it started acting-up. I'll have to jack this BAD BOY up and see if they forgot to tighten something! Thanks RON
Hellauva way to find out you are having a problem......No brown stains on the seats after that little side to side motion at speed I hope. Had my Riv develop a vibration issue at 90 and higher and it was a balance and tire issue.....
Ask, LARRY70GS & BILLMAH52 if they had to change their shorts. They were behind me when we were going to E-Town for the N.E.Buick races. A Corvette came-up behind us on a 4 lane highway at a high rate of speed, I was the leed car in our group and thought I'd show the 'Vette how he 'aint commin' by some Buicks.....so I pulled it out of O.D. & slam-it to the boards and off we go (done this many times before). Me and the 'vette are well over 100mph and my car starts swayin', couldn't get it to stop, finally under 100 I gain control. At the next gas station we all pull in and Larry & Bill said they thought I was a dead man. They never saw a car go out of control like that before. Scared the Crap out of all of us!!!! The car has been in the garage since then and i haven't had a chance to look at it..........but I sure will NOW!!!!!! ou: ou: ou:
yep Went through the same thing with my skylark. Checked everything except tires, turned out two back tires were off 4 grams apiece. Had them reblanced and still did same thing. Went and bought 2 new tires and havnt had a problem since. Turns out the tires had bad flat spots in them and couldnt be balanced and saved.
