I've been getting a lot of vibration at high speed (70& above) Did a site search & decided to start with the driveline. I took the driveshaft to the local driveline shop, Inland Empire Driveline & they pointed out that both ends of the shaft don't line up with each other. Approx. 20 degrees offset. Is this normal? Also they say the driveshaft runs out about .050 . What is acceptable tolerance ? I believe the shaft to be original,(#'s car) and they want to replace the pipe, and match both ends. Another guy there says GM offset the ends for harmonics, does this sound right to anyone? Any help would be appreciated, Thanks, Terry

Can't help with the run out specs but when I had my driveshaft shortend they showed me up front that it was "15deg out of phase" as they called it. They said this was something Chevy did with the Camaro to help eliminate vibration. They also said that it would be reassembled in phase or in line as I would call it. I've had no problems with the balanced in line version.

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Robert Johnson

'69 getting better every day... (every pay day)
350ci 700r4 3.55 posi

[This message has been edited by rojo (edited 12-19-2001).]

Thanks Robert, I was'nt sure whether to believe these guys, they have been around for awhile and advertise in a lot of hot rod mags, but they did'nt sound to sure of themselves, and seemed way to eager to cut up my driveshaft! May just a misperception on my part. Terry

Gm did it for a reason, and yes, it is to cancel out the vibration at the zero degree of power transfer.

Power traveling through an U-joint is like a sine wave, the positive portion pushes the driving yoke against the driven yoke, the negative portion pulls the driving yoke against the driven yoke. When two joints are lined up on the same plane, the two sine waves are superimposed over each other, in-phase, the term is called.

At the point of every 90 degrees, there is an equilibrium of pushing/pulling, thus, the U-joints are loose, no power is transferring. GM went and offset one joint by 15 degrees to keep the joints under a constant load, thus, no rattles, no shakes.

Remember the example above, we taken one sine wave and moved it about the X-axis by 15 degrees, no equilibrium point now. Driveshaft is always under tension.


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Everett 68/350/PG/11.90/115mph

Everett#2390 very impressive and interesting
description!I always knew the two joints ran at different angles to cancel each other out but never knew about the 'offset'of the ends.You learn something new every day.

thanks guys, your explanation makes sense, you've been a great help. Terry