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Discussion Starter · #1 ·
I have a '96 LT 4. When you take the top off, it has a major vibration & relly handles bad. It doesn't when the top is on.....:WTF ? Haven't changed anything like wheels & tires...they were just fine. It just started doing it on it's own. ANYONE got any ideas:huh: ????
 

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I would check the frame and body real close. It sounds like you are losing you Chassis rigidity when removing the top. as though the top is holding every thing in place. you lose a little when removing the top but it should not effect the car that much...
 

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I had the same problem maby not as bad as you say but like the same thing. it is just the way the car is made the convertibles have corss frames not the coupe. You can by a corss frame from r-d racing. I wanted to by it but funds are low right now for that. they say it takes car of the bad ride.
 

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You've got my curiosity up. I've got to go topless and see what happens. Hard to believe they become a flexy flier without the top. (I know my Olds Cutlass T top was flexy all the time.)
 

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I have a '96 LT 4. When you take the top off, it has a major vibration & relly handles bad. It doesn't when the top is on.....:WTF ? Haven't changed anything like wheels & tires...they were just fine. It just started doing it on it's own. ANYONE got any ideas:huh: ????
Is this is NEW condition? Or did you just recently buy the car, and this is your first experience with the targa top out?

Here's the scoop: When Chevrolet Engineering had completed most of the structural design work on the C4, Lloyd Reuss (a GM VP at the time), saw the car. He liked everything except for the t-top (with the support bar), and informed the design staff that he wanted a targa top, not a t-top. At that late stage of the game, design didn't have time to redesign the structure to compensate for no support bar.

Consequently, when you remove the top, there is additional flexure in the chassis, which can be felt in the seat of your pants as well as in the steering. In mine, there is a low speed oscillation of the steering wheel in the horizontal direction (but not in the vertical). The car also displays much more in the way of squeaks and rattles, and just doesn't feel as planted.

However, once I've driven it about 15 - 20 minutes, I get used to it (muscle memory, I guess). I've considered the cross brace, and there are a couple of companies that make a bolt in targa truss that are supposed to significantly reduce the vibration (r-d racing makes one, and I don't recall the second one right now).

If this is a new problem, then, as iburke suggested, you need to figure out what broke underneath the car.

Steven
 

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Discussion Starter · #6 ·
I've had the car a couple of years. It just started one day...it's not like I race it or even drive it real hard....well, sometimes maybe i do get on it, but it's usually in a straight lin, more or less, like getting on the interstate. I do have a guy looking at it now, but maybe this is something I should take to the ...ugh!...dealership???
 

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You've got my curiosity up. I've got to go topless and see what happens. Hard to believe they become a flexy flier without the top. (I know my Olds Cutlass T top was flexy all the time.)
It's what they call Cowl Shake. You ain't gonna like it. Don't take the top off anymore.
 

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Discussion Starter · #8 ·
Cowl Shake??:WTF ??:thud: What can be done to fix that..:lookinup: ..it hasn't always done it...just started one day.
 

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East of the pond they call this scuttle shake. I've driven converts with this. Over rough roads it feels like the car is coming apart at the seams. I'll not remove my top. Thanks for the warning.
 

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Cowl Shake??:WTF ??:thud: What can be done to fix that..:lookinup: ..it hasn't always done it...just started one day.
If you have been driving with the top off & experienced a change something could be amiss.



If that's the case then you better check it out.

I don't take the top off my 95 anymore..hate the ride quality.

I'm thinking of getting a brace that bolts onto the top to replace thee targa.



They are made by R&D I believe.
 

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Discussion Starter · #11 ·
SO...just what is it that could be wrong??? Is something broken??? Bent? ANYONE got any IDEAS on what causes this????
 

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Discussion Starter · #13 ·
With the top on, it handles like a dream....:partyon: or like a 'vette should. It only "shakes" when the topp is off. Tire pressure is fine, all the weights are on the wheels. I am baffled....:thud:
 

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Those of you who have this shaking problem, how many miles are on your Vette? I have a '90 with 100K and its still as rigid as new. I do race mine, but always with the top in at high speed events. I have done maybe 1 or 2 autocrosses with the top off but nothing has seemed to effect the car. Is this something I should expect to happen soon?
 

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Discussion Starter · #15 ·
I have approx. 98,000 mi. I do not autocross. Just enjoy driving, with the top on , now. Would like to enjoy it w/the top off once again.
 

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Discussion Starter · #16 ·
Hey Grumpy....got any ideas on this. Your input would be extremely welcomed. I have seen your posts & you always offer good advice...:thumbsup:
 

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Cowl shake

I know you said you checked your wheel weights, but how long has it been since your wheels were balanced? As tires wear, they may need to be re-balanced. I think you're on the right track with the thought of the tires being a little out of balance. Be sure you get a good dynamic spin balance job, not just a bubble balance.
 

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Removed the top off for the first time today and it was one hell of a ride home.

She was shake rattle & roll all the way. It was doing some resonation inside at any speed above 35-75 (didn't go fast than that with it off).

I put it back on and smooth as silk again. Not that big a deal it's good enough for the beach at 15 mph. Otherwise the tops staying on.
 

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when I take my top off I crack my both windows and vibration goes away..I got the rear hatch vent part coming so I'll see if it helps...the Fall is coming and the top will be coming off more..Ride on guys..:thumbsup:
 
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