ive got a 91 bird that develops a nasty vibration at about 90mph, its so severe i back off as im afraid to see what happens if i go faster, the whole dash shakes like crazy......i have an aluminum driveshaft from dennys, he seems pretty good with that stuff i doubt thats it.............i had my wheels and tires done on that hercules road surface machine last year , cant remember the name of it now, i dont recall it being that bad last year, i did have my pinion angle checked and the guy said it cant be off because of the tourque arm..............my car does sit all winter and this is the first time this year i got it up to that speed.............should i have the tires and wheels done again? im thinking maybe the tires get flat spots in them from sitting all winter that doesnt work it self out? also what is this on car balancing i read about? and where could i get that done? perhaps thats the way to go as i assume it takes into consideration the rotors and drums , ive never heard of this tho

 

alignment?

 

Could be a number of things, but if you KNOW it was good last year @ those speeds, then it probably is tires. Be a bit cautious -- I know what it feels like to have a tire blow @ 70 MPH due to it sitting for too long. Also took a bit of the fender with it as well...

 

mmmm i would think the alignment would have to be pretty far out to cause that no? it doesnt drift at all..........im interested to find out more about this on car wheel balancing, wondering who does it , im about 2 hours north of nyc .............that was a hunter gsp 9700 machine , not hercules i was referring to

 

If it's a high speed vibration like you're riding inside an electric shaver then it's driveshaft-related. On 3rd and 4th gens I've had good results by just flipping the driveshaft 180* on the pinion yoke. I had a 3.5" aluminum shaft from LPE that would vibrate badly when installed one way, but smooth as a baby's butt up past 130 when installed the other way. My success rate on this is about 50/50. Hey, it's worth a shot!

If it's a lower speed vibration like you can feel the individual vibrations then it's more than likely wheel-and-tire related or worn out suspension parts.

 

nope all suspension parts are new, kyb shocks and struts, eibach springs in front............hellwig bars etc., mmmmm im going to have the driveshaft looked at, i think the best is to have them balance it with the yoke on and replace the seal in the tranny tail cone?, and replace the universals, i could buy them myself, what are the best to get? and what exactly would i need to ask for at the dealer for this seal in the tranny cone? i have no vibration until about 85-90 ........

 

I have the same problem with my 91 at about 100 wy ex wife would have loved it but it scares the hell out of me.

 

 

welp im going to get to the bottom of it, first im doing all 4 tires on the 9700 machine, then if its still there ill tackel the driveshaft............ill keep yas posted

 

well, its apparently a flat spot in the tire from sitting all winter, i had 2 of the 4 tires done on the gsp 9700, they said one of them was within spec , he said the limit is 27? i think this is psi the tire exerts on the machine? maybe somone can enlighten me as to how the machine works and what the number means..............so one was 27 he didnt touch that one just balanced it, the other was 46 and he could only get it down to 35 , said the tire has a flat spot................so i put the 27 on the front and the bad one , 35 on the back , now with not even touching the passenger side tires yet, the vibration is minimal at 100 mph.................=) i wont go much faster without a driveshaft loop, btw , who sells the tourque arm with the loop built in for the 91 bird? spohn?

 

I'm telling you now...you REALLY should replace that tire. I've had them blowout from sitting over the winter. The tire's rubber compound has certain chemicals spread throughout it that replenish the rubber's flexibility and makes it more resilient, but this only occurs when the rubber is flexed (i.e.: driving down the road). If you let a tire go too long without being flexed and then suddenly drive it, chances are a lot of times pretty decent that the tire will blow before this "self-reconditioning" has a chance to take place.

If it's gonna blow, it wil more than likely be at speed and within the next 1000 miles. It's up to you what you want to do; just looking out for ya. I wish someone had warned me before I experienced it.

 

really? anyone else care to chime in on this?

 

so noone knows how the hunter gsp9700 gets it numbers and what they mean?

 

nobody?