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Discussion Starter · #1 ·
Hello, I just got a used aluminum drive shaft and the ends had been replaced. The steel one on my car had like a balancer/black donut thing on the front where the drive shaft goes into the transmission, but the aluminum didn't have one. I tried it out and when I start going over 65-70 mph the car starts shaking, so I currently can't get in the freeway without it shaking. Would just getting the drive shaft balanced at a shop solve this problem or does it need that thing on the front to work properly? And of course that's if it wasn't damaged but it looks to be straight, just unbalanced.
 

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Ramblin' Wreck
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I recently had a new steel driveshaft made and the builder did not install a damper on the front like the original, said it wasn't needed. I don't have any vibration without it. But I don't know if that is ok with an aluminum one.
 

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Discussion Starter · #3 ·
Hmm okay. I guess it should be good then. Just needs a balancing. I'm guessing the person who changed the ends on it didn't get it balanced, and I'm sure it has to be balanced when the ends are changed.
 

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The "ring" is a harmonic damper, not a balancer. The driveshaft can suffer from vibrations based on the "critical frequency" of the specific driveshaft. The 3.8L V6 adds to the problem with its quirky counter balance shaft in the engine. Maybe the V6 DS needs that damper.

The LT1 V8 cars had the damper, but still had a problem with the steel driveshaft reaching critical frequency when the driveshaft RPM reached a certain value. Massive vibrations. Most people never got the DS moving that fast, unless they swapped in 3.73 or 4.10 gears. The problem was so bad that GM issued a technical service bulletin (TSB) that allowed many people to get a free replacement aluminum DS, if the car was still under warranty. The aluminum shaft has a higher critical frequency (RPM).

Given the fact that the aluminum shaft has a higher critical frequency I would have it checked for balance, or possibly the centerline of one of the "ends" not being concentric with the centerline of the tube. Others have swapped the aluminum DS into the 3.8L V6 with no problems
 

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Discussion Starter · #5 ·
Yes, I've heard of many people just installing it and done, but this one has had the ends replaced so it probably got unbalanced or one of them not being centered like you said but the person didn't care or somehow worked for him. I'll get it checked out. ...Well after we change the cross, because the junkyard people didn't bring it with the caps that go on the cross, we just bought another cross and put the caps on the one on the DS, it might be throwing it all off because they may fit but are not the right size for it. Since we had to buy the whole thing, I might as well change it. New parts are always better.

I didn't think of that when I asked this, could not using the original caps on just the cross make it vibrate?? Sounds crazy, lol.
 
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