Driveshaft causing intermittent vibrations
 

Hey guys and gals,

To keep it short, just installed an OFH, Perrin 2.5 res cbe, Dss aluminum driveshaft and JDM underpanels today! Loving the new setup, but I do notice a few occasional short, sharp vibrations through the gas pedal when turning on uneven ground and accelerating. Feels like when ABS engages. I'm not too concerned about it, as the cbe settled cockeyed so I have to adjust the tips; but I'm thinking the driveshaft is moving about a little more (since it's a 1-piece vs the oem 2-piece) and it's probably rubbing on the under panels near the driver footwell. Just thought I'd get your thoughts for anything else it could be before I take a look in there tomorrow. Thanks for the input!

Both steel and carbon fiber are better at dampening vibrations. Factory driveshaft is steel IIRC.

I noticed this while looking into building my road bicycle. You'd see a lot of aluminum frames to save weight, but they'd have CF forks to dampen vibrations. Then you'd see all steel frames, steel forks as well. Or all CF for those with $$$$$

If anything I would imagine the 1-pc driveshaft moves around less than the 2-pc.

True story! I don't mind the extra vibrations, since the AL unit is half the price of the CF one and the cf is only about 1lb lighter. Plus I dunno, makes it feel more "racy". I'm weird in that I like my fun cars to be slightly uncomfortable like that.

My bad with the word choice, I didn't mean to say the AL shaft is actually moving around more, I mean more like there could be more play between it, the diff and the tranny on a sharp turn. My thinking was the factory one can flex at the joint so it copes a bit better with that sharp turn/accel scenario, where the AL one shifts slightly but just enough to rub one of the underplates. I could be way off though, wont know for sure till I get under there.

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I have a CF one and I think I know what you are talking about. I think it's related to spin of the rear wheels - happens most noticably when you accelerate hard from low speeds especially on wet asphalt and at harsh turns when the car suddenly goes sideways a bit but before the traction control engages. My feeling was that it happens because the DS-differential connection point shakes a lot in stock bushings w/o a differencial brace and it feels much stronger than with the stock DS because of the 1-piece nature of the aftermarket one.

You can turn shaft 180 degrees on diff plate and try that to see if vibes etc are less. With Alu shafts this is common. It's either by luck best on 1st bolt up or spin it 180 and try again see if it's less.

If you have a vibration with a lot of steering input at low speed (like taking off after backing out of your driveway), that's the diff doing its job, nothing to do with your driveshaft.

I have a driveshaft shop aliminum DS on my car, and it makes a little noise in first and part of second if I'm cheap with the gas pedal. I'm pretty sure its the syncros being amplified through the aluminum. I have no vibration though? Even at 120 no vibe.

do you have any poly or solid mounts in the car ?

no all the bushings are still OEM

Thanks chaps for the replies so far! going to try turning the shaft (...LADIES...) and some have suggested checking the bolts/clips on the underpannels as well. I live on a somewhat rutted gravel road so I wouldn't be surprised if that loosened something up down there.

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It will give you nothing. Turning the shaft is the solution for vibrations on high DS rotation speeds.

Took it for a 3 hr drive today, and I think this is right on the money after spending more time with it. Its exactly as you describe, happens durring cornering with either high throttle or sharp turn in, and before the trac light kicks on. All the bolts underneath are good, and I didn't bother turning the driveshaft since I don't experience the higher speed vibrations. At this point I'm happy to say its normal, and I love how much smoother the driveshaft makes gear changes, plus the quicker revs. Great bang for the buck mod!

/thread :D

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