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Discussion Starter · #1 ·
I really need you guys help. A few weeks ago while starting up in first gear from a traffic light (normal traffic light easy start!), I experienced a loud jolt/thunk in the rear of the car. It was so forceful that I thought I had been tapped by another car. No one was behind me at the time. It felt like somebody had hit you doing about 5 MPH! Yesterday it happened again. Only jolt as even stronger. Snapped my head against the seat! Before I take it to the dealer I thought I would ask you guys if any one has had the same experience. I figure if it does it some more something is going to break. I have 2400 miles on the car and it has been absolutely perfect otherwise...I love this Vette! Any ideas?

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Bob
2001 SW/Mod Red Z06 With Z06 Plate on Right Rear
1978 Silver Anniversary
1993 Torch Red Convertable
1996 Grand Sport
1990 SS 454 Chevy Truck
 

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Sounds fuel related to me because mechanical would bind and slow not accelerate..... just a guess. I had this happen on another chevy and it was carb related way back then. Float was sticking causing raw fuel to ignite in my exhaust with a thunk noise and burst of acceleration.
 

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HI there,
Questions please, do you have the same noise when you let the clutch out in the other gears?????? Or is it strictly in first only??
Does the clunk get stronger when you put more throttle into it???????
Please let me know, c4c5
 

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Discussion Starter · #4 ·
Hi: C4C5 Thanks for writing back. This thunk has only occurred twice. Both times in first gear only. Both times from a light start (I was in the parking lot at Blockbuster the first time it happened!) But the force of the occurance was in my estimation the same as getting hit in the rear at 5 MPH. My basis is that two weeks ago I got tapped in the rear of my Cadillac DeVille which did about $1000 to the bumper and inner fender and the force of the experience and the feel was almost identical in the car. The car drives, shifts and makes no other abnormal sound in any other gear. My wife drove it for the first time last night and I road with her and listened and everything sounds and feels absolutely normal. The more I think about it the more it feels like something is happening in the rear trans...but I don't know. I know that the car began rolling when the thunk/whump happened. The force is so strong, I am convinced that a few more occurances and something will break...then we can fix it assuming that the breakage and the cause are the same. I am trying to get to the root before I have any serious damage. I drove the car this orning and did notice that when stopped, that from neutral to first I can feel three distinct "detents" as I push the shifter forward into first. I am wondering if I thought the lever was already fully forward when I was at one of these spots and only partially engaged. Is this notchiness normal in the shifter? Thanks.

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Bob
2001 SW/Mod Red Z06 With Z06 Plate on Right Rear
1978 Silver Anniversary
1993 Torch Red Convertable
1996 Grand Sport
1990 SS 454 Chevy Truck
 

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Sounds like it popped out of gear to me. This can be forceful enough to jolt the car...

The one time this happened to me I freaked!

Was the trans still in gear after the jolt?

JC
 

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Discussion Starter · #6 ·
JC: Don't know...through in the clutch and immediately looked in the mirror to see what hit me.

Did I pass you on West Ox road this morning? Black Z06 was heading towards Reston. /phpBB/images/smiles/icon_smile.gif
 

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Had it happen to me about a week ago, but it had popped out of first gear when I let the clutch out. Loud as hell and scared the crap out of me. Thought I had hit something. It was extremely violent!! /phpBB/images/smiles/icon_frown.gif
 

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Discussion Starter · #9 ·
Thanks Frank...I was beginning to think I was the only one who had experienced this /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif It is truly a violent reaction in the car! /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif May be C4C5 can give us a clue as to what is going on. I have the stock shifter and I know you have swapped yours for another type /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_smile.gif
 

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Well,
Here is how I would proceed, did the clunk feel like it came right through the shifter, or is it more through the seat??
Attempt to duplicate this through the exact same location, and see what happens.
Also, jounce on the rear facia to see if you hear any squeaking in the back.
Please let me know what you find, c4c5
 

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Discussion Starter · #11 ·
C4C5: Defintely Seat....no squeaking....just went and checked it. Second time it through my head back against the seat top...felt just like I got hit from behind. /phpBB/images/smiles/icon_eek.gif

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Bob
2001 SW/Mod Red Z06 With Z06 Plate on Right Rear
1978 Silver Anniversary
1993 Torch Red Convertable
1996 Grand Sport
1990 SS 454 Chevy Truck
 

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I'm pretty stumped on what might be the problem but let me ask you this. Have you raced the car or given it any hard driving and tire spinning. I know my blazer doesn't compare but i had a similar experience with it and it ended up being broken gears in the rear end. You might wanna take it in and have them check the rear differential. Just a though but let us know cus id like to know what it was.

RedZ
 

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ok, well Red makes a good point, is it only in a straight line???
Honestly, I think that either a mount is loose, or a suspension components is loose in the rear subframe area.
You see, if it was in the driveline, your clunk would transmit down the driveline, like a stethescope.
I am more biased to a suspension component in the rear end at this point, and would suggest that when you appoint at the dealer, take the shop foreman for a ride to confirm the noise, just so you cannot be told that they dont know what they are looking for.
Please keep us posted on what you find, c4c5
 

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Discussion Starter · #14 ·
Thanks for the help guys...no racing...no wheel spinning...I turn 40-10 in age next weekend. /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_eek.gif My tech here knows me and my cars...they are always babied! I will let you know what I find out next week after he has had a look at it.
 

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I have experienced the jolt at least 5 times during the year. The jolt was from the car slipping out of first gear. Everytime it happened I thought a car hit me from behind.

Craig
 

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I'm out of advice then. If you haven't caused your tires to break lose then grab traction again then i doubt its the rear end. c4c5 had the best idea though. Go to your dealer and have their corvette guy in the mechanics shop go for a drive with you.

RedZ
 

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bstein,
did you fidn out what was the problem with your car yet. Im curious to know so i'll know what tyo expect when i hear that crap on my car.

RedZ
 

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I had this happen Saturday August 11th. I have a good grade on my driveway. I backed out of the garage to the end of my driveway and put it in first to pull back up the driveway to wash it. As I gave it some gas the I heared the clunk and looked just in time to see the shifter pop right out of gear. I put it back in gear and continued up the driveway. I did not take it for a drive but I had to repeat the process to put it back in the 3rd stall and did not have a problem.
 

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I think I experienced a similar condition. I was pulling out of a parking lot going about 5mph in first gear, got to the street and had to push in clutch to slow to a crawl to wait for traffic, still in first gear. While still rolling I eased clutch out in normal manner and started moderately accelerating in first gear. A few seconds after my foot was off the clutch, and I was accelerating a bit faster I felt a definite jolt and heard a clunk as if the clutch, or something, had been slipping a little and then finally fully engaged while the engine was gaining RPMs. At first I thought I had driven over some pebbles and one or both tires spun a bit then caught, but to get that amount of forward jolt the tires would have had to have been spinning rather quickly and then all of a sudden regain full traction. But I got no TC or AH indications on the DIC, and I don’t think that simply spinning the tires and regaining traction would produce the clunk I heard. And the shifter definitely did not slip out of first gear. My hand was on it the entire time. My M3 used to slip out of first frequently, so I developed the habit of holding the shifter in first.

Does sound similar to what you experienced?

c4c5 How does this sound to you?

Mike
 

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Hi Mike,
As for what you are saying, it seems to me that because you are holding the shifter, it would definately know it if it did pop out.
Honestly, yours sounds different than B, as you do not specify if it was over bumps, but I think that you would if it was.
I would ask to see if you can duplicate if you attempt it down hill.
Have you had a shifter adjustment??
Best to you, c4c5
 
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