Towards the end of acceleration when my car is about to downshift , it starts to shake terribly .Sometimes does not stop until I take my foot off the gas and start to slow down 1 mph or so .It seems like it starts shaking from the back then works its way to the front fast .It first started doing this about 8 months ago , it has been checked by a mechanic several times , but they can't find anything .But now its gotten to the point where its so bad that it does it every time I accelerate and it does it for longer periods of times .And more often I have to take my foot of the gas and slow down a tad bit to get it to stop .Anyone have a clue to what it is ? lol Thanx in advance , Wayne

 

The description is not totally clear.
Feel it in your butt, the steering wheel, the wheels shake, what?
I discovered what is the problem with my Wife's 1968 Camaro. Front bearings were loose, rear shocks were bad and the wheels were outta balance.
I'm not done yet.
The front drum brakes grab & chatter (I'm switching to discs when I swap in my other coils from my 1967 Camaro & the new gas Gabriel shocks-the car gets multi leafs and a 12 bolt one day later on).
I replaced the rear shocks and alot of driving vibration ceased.
BUT, this is with 1968 technology, I'm working with. Same thoughts different platform?
Driving this under same conditon everytime?
Same road?
New tires?
old tires?
Lost of varible come into play, narrow the varibles down (roads, speeds, etc) and keep running the thoughts of solutions.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

Karl ,
I have new tires , there balanced .
does this on the interstate , on hwy , backroads. I have new front shocks , The shaking feels like its shaking the whole interior on my car and when it shakes Im wondering hmm wonder if the outside is shakin this bad to , and if it is how ridiculous an i lookin i dont feel the vibration in the steering wheel but it shakes it , like the rest of the interior is shaking .Hmm I was just wondering , I wonder if this could be a bent driveshaft or soemethign with that nature Karl ? Thanx in advance , Wayne

 

Also , I dont ever re-call it shaking like when im in my neighborhood taking off at a lower speed or driving on campus at school , Thanx , Wayne

 

Dude, get it up to speed, then throw it in neutral....if the vibration goes away, you need to get a new drive shaft.

 

Damn..u beat me to it.. yea to what he said.

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1989 Firebird. Modded.
My car is currently listed on ebay:
http://cgi.ebay.com/ebaymotors/aw-cgi/eBayISAPI.dll?ViewItem&item=594662251

"I'd rather run last in a full out race, than to NOT have run at all"
#3 Forever

 

Never thought about that , that's a good ideau though .I'll try it today , Thanx Ovrclock350 ......Wayne

 

It could also be axle bearings, they sometimes vibrate but usually growl. Could also be a bent axle (unlikely but a posibility) or tread separation in the tires, I know someone that had brand new tires do that to him once (not Firestone).

You may also want to jack up the rear end and run it at speed to rule out front end probs.

My $.02
Dale

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1986 FireBird
2.8L MPFI
1/2 CAI
Gutted Cat, No muffler
Was 700-R4 --> Now T5

Great cars aren't bought, they are built