I seem to remember someone talking about driveshafts being out of balance and this being a common thing. Is this true, or only for high performance cars like ours. I have a vibration at 80 mph that I can't pinpoint and I thought the driveshaft might be it.

Any help?

Thanks

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1989 FIREBIRD FORMULA 350
K&N, ACCEL CAP & ROTOR,
FLOWMASTER AMERICAN THUNDER CAT-BACK

 

All drive shafts have natural harmonics that become aparent at high speed. Even balanced driveshaft will begin to flex with a sinusoid pattern. This flexing is entirely dependent on driveshaft length. For instance Trucks and SUVs have lower speed ratings than Camaros because of the shorter shaft. Lightening the shaft will help(aluminum or Carbon Fiber$$$$$$$$). What generally happens is that the U joints blow out because of the large angles that the driveshaft makes during flexing. As for the 80 mph vibration. I'd blame tires, rotors, and drums before driveshafts.

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'87 Bird 350 .060 over 700R4 + Lots more

 

you will know it's your driveshaft if you
drive at a speed where you can downshift into another gear (without red-lining your tach )too much, and then downshift.. if you experience vibration when you downshift because of the higher rpms then it is your driveshaft.

 

if you down shift that makes no sense! The drive shaft is still spinning the same speed! The motor will rev more because all you did is change the speed in the tranny. Mine has the same vibration over 80MPH. It is a pulsing vibration that runs right though the car. I deal with it because I am too poor to fix it

 

Have the tires and wheels balanced or rebalanced--make sure the shop checks for any wheel/tire problems. Where I used to work, we rebalanced tires every 6000 miles for free. We did alot of volume and I never saw a set of tires that didn't need the balance(checked them before the weight were pulled off). This may not be the problem, but it would eliminate a possibility.


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, current red metallic paint. Lots of other stuff...
82camaro

 

What gears do you have? I swapped to 3:73's and have the exact same problem as you. I guy on the camarox28.com board was having the same problem, checked wheels and all that other jazz, still had the problem. He then bought an aluminum DS and it went away. I have read that 92 MPH is exactly half the DS terminal velocity (with 3:73 and an A4) it could be that since your getting close to that speed it is starting to vibrate like it would at 92 MPH. Check the cheap stuff first, then get a new Al DS.

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• 89 Formula 305 WS6
  SFC's, LCA's, Air Foil
  Spohn Panhard Bar
  Flowmaster Cat Back, Tranny Cooler
  A/F Ratio Meter (not a mod but it sure spurs interest)
  Trans Temp Gauge
  Most "Free" Mods
  3:73, Zexel Torsion Posi
• 90 Eagle Talon 2.0
  (Winter Beater)
  Mods? Um, no
  Its for sale!!
  Email me if you need a decent back up car

 

3.27 POSI REAR,

I just put 4 new tires on the car last week, everything up front is tight, as far as I can tell. u-joints were checked and are good. I wanted to get a Alum. DS but it is lower on the wish list right now.

thanks

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1989 FIREBIRD FORMULA 350
K&N, ACCEL CAP & ROTOR,
FLOWMASTER AMERICAN THUNDER CAT-BACK

 

Dont forget to check the axle. I had the same problem and it was my axle. Next time you have the rear wheels off the ground start the car and put it in gear then have someone look at the wheels if your axle is bent it will show.

 

i got an alum DS and all my vibrations went away, i mean all. the times when i go anywhere from 80-140 its smooth just the wind holding me back.

and anyways, why would you need to be going 80mph+ thats illegal, and we are all legal abiding citizens!!