Haha. Anyways, I was driving on the freeway earlier today, and once I hit 70-75 mph in od, my car got a BAAD vibration... I've noticed it before - but I don't think it's been this bad before... What could the cause of this be? I than took it out to a road in good condition - with very few cracks and stuff in it, and kicked it up to 70-75 mph again, and the vibration was still there. (I thought it may have just been the condition of the road.) The vibration gets so bad that the dash will vibrate - the cd player will skip - and you can just generally feel it throughout the car... But it only happens at that high of a speed.. My tires are pretty new - only 3k miles on them or so... So, I know that's not the cause. Anyone else got an idea? Or is it just the face it's a "con" on owing a 3rd gen.? Btw, it's an 84 Firebird SE 305 automatic... For those who can't read the user info. Thaaaank you... <333

Is the slot where you stick the quarters in stuck?

Seriously, I've had brand new tires have treads separating, don't rule it
out. I'd take a close look at your driveshaft and trans mount.

even though your tires are newer you could have lost a weight and now they are out of balance, have them checked for high speed balance again, rule this out then start looking under the front end for an issue, this has nothing to do with the interior other than the fact that Fbody dashes do rattle

mine did the same thing when i got it but i put it up on the lift and the sway bar bushings were gone in the front and back. i swaped some poly bushings in there and it helped alot. also it could be the tires arent balanced correctly or bad shocks. make sure you check all that out.

my guess is it's the transmission/tranny mount. my transmission has been acting up lately and i've been noticing alot of vibrating too. i'm gonna need to buy a new tranny soon. it slips real bad

from a discount tire guy of nearly 2 years...its not your tires...tires being out of balance and EVEN separated arent going to SHAKE your dash....youd feel the steering wheel shake and move and possibly a shake in your seat but if the DASH and entire car is shaking look elsewhere for your problem

if the tire separation was really terrible it might be possible but ive nev heard of anyone tellin me their dash and entire car was shaking that bad and ive seen some messed up tires

Your tires can cause dash to shake. On my friends 88 camaro his front tires had flat spots in them. It caused bad vibration at anything above 55.

When I bought my new truck this past year someone had put some newer model GMC rims on it, but never balanced the tires (I mean no weights on them what so ever) and my entire truck shook at any speed over 65 mph.

I'm not saying it couldnt be any other problem, just something to check
Matt

Like the rear tires... that aren't connected to the steering...

This is the wrong forum for this anyways.

So, I'm taking the car in tomorrow to get the tires balanced out and stuff...

I know, or at least pray it's not the shocks, struts, front and back sway bar bushings b/c all that got replaced like... two months ago, at the very least. LoL.

But, I will check that stuff in the morning...

I'll go ahead and have a pro do it, lordy knows I'm not one at all...

Ummm... How can I move this to the right forum?

I'll post tomorrow afternoon and let people know!

Thanks guys for the answers to my questions...

<333

Check the universal joints on the propshaft too (driveshaft in USA?) - if one or both of those has worn then it will cause severe vibration at relatively high speed.

It would be wise to give everything a good once over first.

Busted belts/out of balance tires will make the wheel shake if its on the front. If u get a weird feeling in your feet/calves or get the feeling of a floor board'ish vibration its on the rear. It would have to be horrible to make the entire car shake, like a completely seperated tire or severely bent rim/axle. Provided your car has blanced tires from the last time, you would see the severe stuff just taking a thourough look.

70-75mph is usually a drive line type of vibration vs. a tire/wheel/axle issue, which tend to occur over wider ranges of speeds and you can see visually in the case of axles ro severely warped/dented rim/tire.

Especially when it tends to come and go repeatedly at those speeds(meaning at speed it does, but above and below it doesnt).

Check your u -joints out first, I would go so far as to pull the driveshaft and see if its straight and the u -joints are actually mounted to it straight as well. A lot of the metal driveshafts had issues from GM in all car lines from the 80-90's. Even seen some yokes that were fubared as well.

If u need to replace it, try and find a aluminum one or step up to a Ls1 driveshaft. I would recommend any one you replace it with be checked for good u-joints and balanced however.

later
Jeremy

O yea i can agree with the fubared yokes from GM, i tore a yoke to shreds off of a 9bolt rear

like the tires that could be on the back that are connected to the car that can cause the car body to shake....how many years have you spent dealing with tire problems day in and day out

i take back the not possible comment and did say at the bottom that if they were REALLY fed up it could be

I'm having the same problem. Let me tell you what I've done so far with no luck.
Balanced all tires 3 times
replaced 2 tires for out of round
checked all rims for being bent
checked both rear axels to see if their bent
replaced steering box (was shot!)
replaced center link (it was sloppy)
checked all mounts (ok)
replaced rear trans housing bushing and seal
replaced driveshaft and front trans yoke

vibration is still there (slight vib. at 45mph and shaking the whole car at speeds above 65)

new outer tierods going on tomorrow and re-alignment next week end.
What might help me is get someone to drive my car on the interstate while I look at it from my other car. Maybe then I can see what's shaking! If you find it before I do, post it! I'll do the same! It's driving me nuts not being able to find it yet. I've been racing, collecting, and working on cars over 36 yrs. and have never had a problem like this that I couldn't find by now.
One would think that anything that would shake a car this bad would be obvious! After I get the front end straight and it doesn't help, the diff. cover is coming off and the axles are coming out.

The differential input yoke for the driveshaft can be an issue. If it has a small amount of run out the driveshaft will vibrate. Best way to check it is with a dial indicator. I've seen this problem on a couple of vehicles (one being a 3rd gen), with another guy having it written up on his web site (IIRC, a 4th gen, but with an aftermarket rear).

RBob.

I'm having the same issue too. In my case, I believe I was getting vibration from two sources-the driveshaft, and another as yet undiscovered. I replaced the driveshaft and noticed an immediate change in the smoothness of the car at lower speeds (under 65). Whereas before I replaced the driveshaft I would get shaking in the seats, console and dash, I now just have it in the dash, and severely. Definitely feels like something in the front end (and my list of things I've checked/replaced is longer than I care to type).
My next target is the entire front suspension.

i replaced the torque arm bushing and it helped smooth mine out ALOT especialy around 75-80mph