# Vibration Issues at 45mph



## JLINTON (Feb 26, 2021)

2004 GTO 7L Z06 new fully rebuilt motor: max hp 650, new transmission by DND performance magnum performance, when take tranny out and run engine no vibration. Put tranny in run and no vibration, when add drive shaft (one piece) vibration starts at 45 mph and increases where car feels like will fall apart. Still vibrates regardless of how many drive shafts (Steele and alum one piece) are put in. Any idea what could be causing this?


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## BearGFR (Aug 25, 2008)

Well, you now know where the problem ISN'T --- engine, trans, or driveshaft. My guess as to the most likely cause is that your driveshaft/ujoint "operating angles" are off. 
Here's a link to additional information:

https://m.roadkillcustoms.com/how-to-fix-prevent-driveline-vibration/

On our "old" GTO's, we fix this problem by using adjustable upper control arms that allow rotating the centerline of the rear axle "up or down" so that it runs parallel to the centerline of the transmission.
Bear


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## GTO44 (Apr 11, 2016)

JLINTON said:


> 2004 GTO 7L Z06 new fully rebuilt motor: max hp 650, new transmission by DND performance magnum performance, when take tranny out and run engine no vibration. Put tranny in run and no vibration, when add drive shaft (one piece) vibration starts at 45 mph and increases where car feels like will fall apart. Still vibrates regardless of how many drive shafts (Steele and alum one piece) are put in. Any idea what could be causing this?


this is a common and well documented issue with one-piece drive shafts on late model GTO’s. I too had an aluminum 1 piece... Mine would vibrate up around 70. By 100 it was bad. By 120 it felt like the car would fall apart. I sold it and got a DSS 2 piece.

Because of the design of the drivetrain, the pinion angles have to be perfect. But with build tolerances being off slightly from car to car (some would say shitty build tolerances) there’s no gaurantee a 1 piece will work. Its fine in some gtos, bad in some (like mine), and even worse for some (like yours). I took mine to a driveshaft / driveline company and they said there was nothing they could do about it.

Either go back to a stock 2 piece or pony up for the 1000hp DSS 2 piece aluminum/chomoly. The DSS 2 piece is one of the best upgrades ive done on my goat.


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## BearGFR (Aug 25, 2008)

There's another discussion on the topic here

If your shop is telling you that "there's nothing they can do", then what they're really saying is they're not WILLING, or they're not CAPABLE, or that it'd be so expensive they don't think you're be willing to pay for it. 

I'm not at all familiar with the late model GTO's, but I'll still bet a $20 against the hole of a rolling donut that the problem can be corrected by adjusting the angle at the differential. 

It's not rocket surgery 

I found some mentions of folks using shims to change the angle in some cases, depending on which direction it needed to move. 

Bear


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## GTO44 (Apr 11, 2016)

BearGFR said:


> There's another discussion on the topic here
> 
> If your shop is telling you that "there's nothing they can do", then what they're really saying is they're not WILLING, or they're not CAPABLE, or that it'd be so expensive they don't think you're be willing to pay for it.
> 
> ...


thats all well an good but again this is well documented issue with the way the rearend is mounted in the late model gto and the resonance that develops with an aluminum shaft. Ive been on various gto forums for over 10 years. I see this all the time. Thousands of people had this exact issue. The solution is to use a 2 piece driveshaft. Whether stock or after market. Or Carbon fiber 1 piece as it doesnt have the same resonance problem. I would be more skeptical but i personally delt with this issue.


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## SimonKelly (Jun 25, 2020)

that doesn't sound good at all


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