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Discussion Starter #1
I know this has probably been addressed before, but I couldn’t find it anywhere when I searched for it. Does anybody hear a clunk when shifting from 1st to 2nd at low rpm? This is a real annoying sound. Any help would be great.
 

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Discussion Starter #3
Yeah, it's a M-6. Just weird if nobody else is having this problem. I only have a 1000 miles on her.
 

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AmesGTO said:
At low rpm it sounds like some tranny slack. I rarely hear it on my GTO, my V does it a lot. It's not something that can be fixed. Changing how you shift will "fix" it.
I think it can be fixed.... even your V can be fixed, I've heard of this on both of these cars. Try calling the dealership and asking them about the TSB called thunk in the trunk, tell him your complaint and he should be able to steer you to it. If it doesn't fix your car then pm me and tell me to shut up ( :lol: ), and AmesGTO try this link for your problem:http://www.bmrfabrication.com/CTS-Vpage.htm
....you'll need the "anti-wheelhop kit" and the "pinion support brace", and if you want to be cool get that strut tower bar! :cheers
P.S. The T.S.B. # for the "thunk in the trunk" is #04-03-09-003A ! :cheers
 

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The thump in the trunk is under a hard launch. I had one fixed on my GTO. The tranny slack problem is different, it's low rpm and it's a clunk in the drive shaft; this is what it sounds like raven is talking about.

The GTO rarely does it, the V is really easy to do it because GM put some rubber parts in the drivetrain. There is no fix on the V even though it's really bad. It's probably the #1 V owner complaint.

I decided not to try and get the wheel hop out of the V. GM has been denying broken diff claims on V's with BMR parts and GM's fix doesn't look very good to me. The V is my daily driver so I don't worry about drag times anyway.
 

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Interesting on the "V" stuff, the pinion support should help but if dealers are denying warranty then I'd live with it too. As far as the goat, I've had a few customers that even under "light" acceleration noticed this, I do know what you're talking about on the driveshaft noise, not sure....
 

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Discussion Starter #9
AmesGTO said:
At low rpm it sounds like some tranny slack. I rarely hear it on my GTO, my V does it a lot. It's not something that can be fixed. Changing how you shift will "fix" it.

Sometimes it's not when I shift. I can hear it when I engage the clutch. For example, I'll pull up to a stop sign in 1st and engage the clutch and brake to stop and "clunk". I'm going to contact my dealer tomorrow. Will post what he replies with.
 

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raven1124 said:
Sometimes it's not when I shift. I can hear it when I engage the clutch. For example, I'll pull up to a stop sign in 1st and engage the clutch and brake to stop and "clunk". I'm going to contact my dealer tomorrow. Will post what he replies with.
It's definately tranny slack. That's when it happens, when you press in the clutch. I'd bet a GTO dealer won't know anything about it, like I said it's not fixable anyway. A Caddy dealer likely would know what you are talking about, but they can't fix it either. I usually see it when I'm in a low speed situation and do a slow 1 to 2 shift. But, driving around slow and pressing the clutch in you'll see it. The GTO is a lot tougher to make it happen.

They talk about it a lot here, but I can tell you this thread is a year old and I've still never heard of anyone "fixing" it. I just change the rpm I shift at and how I release the clutch and I don't see it very often now. With the GTO I never really heard it very often: http://www.cadillacforums.com/forums/showthread.php?t=10546
 

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Discussion Starter #11
Thanks for the help. I'm still going to call my dealer and b!tch about it. I'm sure they will give me their usual song and dance.
 

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I've had it with other cars with the M6, namely an LT1 Camaro and my Z06. LT1 was real bad, but that car was a high mileage car. Complained about it in the Z06, and the dealer said it was "Normal driveline slop". Not the best sounding noise.
 

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I sometimes get it in my 05 6sp Goat, and got it alot in my F-bodies. Like stated before, I just watch how I shift. I think it's a T-56 thing.
 

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raven1124 said:
Sometimes it's not when I shift. I can hear it when I engage the clutch. For example, I'll pull up to a stop sign in 1st and engage the clutch and brake to stop and "clunk". I'm going to contact my dealer tomorrow. Will post what he replies with.
After hearing this I agree with AmesGTO, sounds like "slack" in the drivetrain.
 

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Discussion Starter #15
I think it's slack too. Just drove around and shifted around 2800-3000 rpm's and no sound. Still bugs the hell out of me though.
 

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Just got my GTO recently and i here it too. CLUNK, in the back of the car, at first i thought something broke then i noticed that if the car doesnt shift right or doesn't have enough gas to clutch ratio it seems to(like said before) slack or sag in the shift. I started giving a lil more gas when shifting low and off the line and i don't hear it at all.......bigger cars i guess need more gas, to get up and goin....had a 4 banger before, big diffrence in pedal pressure and shifting.
 

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Why is it that my 37 year old Corvette with a Muncie M21 has absolutely zero driveline slack, but my '05 GTO has driveline slack after 4000 miles? I hear it especially when pushing in the clutch after allowing the engine to brake the car. It's so annoying. I've had people in my brand new car ask me what that noise was. I'm real glad to hear it's "normal" and the dealer won't do anything about it. What a crock of SHlT.
 

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Yeah mine does it. So does my mom's '04 BMW 325ci (the car I learned to drive a manual in). I thought it was just a "manual trans" thing. It only does it if i push the clutch in really quick. If I am easy and slow about it, its quiet, and then I can feel the slop when I go into second like in a parking lot. I never really paid it any mind since my mom's BMW did it. I figured if a Bimmer does it, it must be ok hahaha.
 

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Discussion Starter #19
It pretty much seems like alot of us has this problem. My friend's goat does the same damn thing. I even heard it on a new Mustang GT the other day.
 

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vette68 said:
Why is it that my 37 year old Corvette with a Muncie M21 has absolutely zero driveline slack, but my '05 GTO has driveline slack after 4000 miles? I hear it especially when pushing in the clutch after allowing the engine to brake the car. It's so annoying. I've had people in my brand new car ask me what that noise was. I'm real glad to hear it's "normal" and the dealer won't do anything about it. What a crock of SHlT.
Sad to say but here's what the reason for the clunk really is!
It starts with the clutch being almost 12" in dia. then working its way back into the gearbox which has 6 count, them forward speeds and a reverse speed gear all are rotating mass's, when you shift gears you are changing the speed of all of these components that ride on needle bearing (unlike your 37 year old M21).
Then you add the increased center distance of the transmission itself and the extra face width of the gears for the added strength and you have a much higher degree of what we call reflected inerta.
It then transfers back down the driveline and the sound enters the car through the rear axle mountings. (AKA junk in the trunk.)
We as transmission engineers (I was one with GM) spent millions of $$$$$ trying to reduce driveline clunk and the the only way to do this is to drive around it, or produce smaller cars with less power and skinny tires with more flexable sidewalls and smaller rotating components. :eek:
By the way your 37 year old corvette has a sliding reverse speed gear thats non synchroized so you really only have 3 speed gears and a smakk rev idler in the clunk path on a 85mm center distance and gears with less then 25mm face width that would never take the torque put to ground with todays tires and engines.
And it screams compared to todays transmissions in gear noise in all gears except 4th and thats only because its directly hooked to the output shaft!

If you think this is BS then upgrade your engine to todays 400 hp 400 lbft of torque and use our new engine management system and add a set of 275X40X18 tires to rear and go do 10, 1/4 mile pass's I'd be real suprised if you make 5 without blowing the clutch or the transmission unless you have a pretty tall rear gear 3.73 or higher! :D
NO we don't make em like we used to............ :rolleyes:
 
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