The 80mph Shake

[JeffD]

Iv'e gotta find out what the heck is going on!
if you accelerate up to and beyond 80mph the beretta bucks awful, i don't think is a motor mount problem because when i step on the clutch it continues until you reach about 75mph. could it be my unbalanced tires? or could it be a problem with my allignment? I told the guys at monroe muffler that if they ran into any problems that they could call me, but of course they didn't. so when i showed up they told me they did the beast that they could. (my original rear sway bar was destroyed.) the car does pull a little to the right, and it feels like i'm always fighting it.
or could it be a sick combo?

[Decipha]

if it pulls to the right chances are your alignment is shot to hell... when i let go of my wheel my car goes completely straight... may want to get your front end realigned, also it wouldn't hurt to get your tires balanced either, would help your 'shake' and possiblyincrease the life of the tire(s)... i hope you replaced the rear sway bar?  i'm curious how exactly does one break the rear sway bar?  mine seems to be pretty solid and i couldn't imagine breaking it in any manner

[JeffD]

man! i dont wanna spend another $50! but if it fixes the problem i guess i'll have to. (why Couldn't they just pick up the phone and call me!)
yeah, i replaced the swaybar. i bought a Z-51 bar and it showed up a few days after i got the car alligned.
i don't know how the bar broke, it was broken before i crashed the car.(it was shattered in one of the corners)

[Jetfoi34]

ok heres what happened with my car
is shook terribly, my front sway bar was disconnected, so i got some end links and it didnt shake as much
got a strut tower brace, didnt really help with the shaking, but handled better
found out there was a loose weight flopping around in my tire, so i broke the tire down, took the weight out, then balanced the tire after i put it back on
no more shaking, i would recommend getting tires roatated/balanced

[JeffD]

i know my front swaybar is connected, and i have some different wheels to put on the front so i'll try that.

[Decipha]

oh yeah this is probably way off but you may want to consider this if all else fails

i had a friend come to me a while back about his car shaking terribly at 55mph, if you sped up or slowed down it went away, just around 55 is shook horribly, I spent many hours replacing other things that we thought it 'could have been' with over $800 spent on parts alone i couldn't even think about charging him labor.  Well a few months after we changed everything the harmonic balancer started making a very high pitched noise, after i replaced the vibration damper the 55mph shake was gone!!... maybe this might help some or at least give you an idea

[Decipha]

btw ^^the car in reference was a 94 pontiac grand am with the 3100

[JeffD]

i never thought of that, ill check it out.
is there any visual way of knowing if the balancer is going?

[rweatherford]

I've had a bad CV joint make the front end and steering shake so bad it wanted to pull you off the road.

[yellow3800]

My shake disappears at 80.

I suspect this: I am using the skeleton shock housing with koni-adj inserts. I suspect the tube wiggles in the housing at the top [there is not cap, just a secure bolt on the bottom], and harmonics play with the car from 60-79ish.

I can move / shake my wheel when its jacked up in the air from side to side almost an inch. this can't be right.

tie rods, inner outer are fine
ball joint and bearings okay
new top strut bearings okay

I'm tempted to liquid fill the gaps of the shock housing with fiberglass resin so it won't shake.

Andy