91TPI5.7

Ok, i was goin up the turnpike yesterday, i jit around 90-100 mph, and there was a vibration. I mean a baaaad vibration. I felt it mostly up through the shifter. Now the guy i bought it from told me about this and when i was crusing around 60-70mph. He was right and it isnt bad, but higher up, is just plain sux. The trans was rebuilt a year ago, and he said that he tried to get the driveshaft balanced but that never worked. Any ideas guys?

Jay 727

Check the driveshaft for dents and the u-joints for looseness. To see if it's coming from either the engine or the drive train drive it to where it vibrates, put it in neutral and let it idle while maintaining speed, if the vibration goes away it's the engine. If it stays the same it's the drive train.
Jack up the rear and spin the tires to check for a bent axle.
Check the wheel bearings for loosness. Get the tires rebalanced, check for uneven tread or separated belts in the tires.

Yvonne

There seems to be a few forum members who can help hear, such as transfixleo. If you still need help, contact him or me directly.

Jay 727

I don't think he needs help hearing..I could be wrong though...

Yvonne

I hate when the software tries to finish my words.
I am legally blind and still typing about 80+ wpm. Sorry...

transfixleo

If all that fails there are some people who had to go to the aluminum driveshaft.

Yvonne

Only put aluminum driveshafts in race only cars. You will regret it in a daily driver!

Apeiron

And why would that be? Lots of people here have them, including myself. They were included from the factory on a number of cars.

Yvonne

From a discussion on www.iroc-zpost.com -

Yvonne: Aluminum driveshafts are lightweight and flexible, good for racing, but more fragile by design.

Sandy: Actually, I've seen 1LE and perhaps G92 equipt Camaros with alum d/s...But, I've heard a lot of people snapping them in drag racing. Road racing is really what they're for. But, and interesting discussion between me and a phd in physics, Bob Hartley offered this rational that:
KE=r^4 in that Kenetic Energy is equal to radius to the 4rth power. Now, alum d/s are larger in dia than steel shafts. (2.75" steel vs 3.5"-4" alum). The increase in diameter is to help absorb and handle the same torque as steel would. But, according to this formula, the radius difference to the 4rth power increases drastically the amount of KE, perhaps more than negating the effects of the alumin weight (alum.5.5lbs vs 12 steel, I think)...But, one does save about 6-7lbs in a race car which can make a difference on the track along with all the other little ways they have to lower vehicle weight. As to radial acceleration resistance, the above formula seems to cancel out a lot of the effect.

Now, folks like Dave Sauro, I think, has a alum d/s. And he may've done dyno runs/track tests between steel vs alum. I know some people have done this, and to my knowlege, the differences in the results were with 2-3HP and 2-3 ft/lbs, well within the error window of dyno test, I think...

Apeiron

That does nothing to explain why you'd regret putting one in a daily driver.

Yvonne

Aluminum driveshafts don't like constant use. The "joints" can break, the shaft can twist... If you drag race, you don't shift several dozen times in a run.

The aftermarket ones are obviously better than stock, exceeding specs. Some stock ones were mentioned on GM's recall or watch lists.

If you are not having any problems with it, do not worry about it. You may want to inspect it from time to time.

tpi_roc

Back to this guys problem


I had a Ujoint lock up at a bent angle going 70mph once...

very bad news, not only did it shake the car so bad that I couldn't use my mirrors to pull over but it dented the chit out of the floorboard of my car, Might want to inspect your U-joints.
If the DS "can't balance" get a new one, aluminum ones are around $125, so no biggy.

slickrock55

The aluminum driveshaft will spin up quicker due to its smaller moment of inertia. There is less rotating mass so it will accelerate quicker. Also, since it weighs less overall, if something is out of balance, it wont make such a vibration as a similarly tweaked steel driveshaft, hence solving vibration problems at high speeds.