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spokejr
07-21-2017, 07:31 PM
Hi all,

I dropped my driveshaft off for some mods (swapping out the Powershift for a T10) and the tech noticed something odd. On my Avanti's driveshaft, there is a slight twist in phasing of the front yoke to the rear yoke, about 20 degrees or so.

In theory they should be in alignment. Is this one of those areas where the manufacturer found that theory doesn't work or was this driveshaft made on a Monday?

Thanks,

Ken

thunderations
07-21-2017, 07:56 PM
Any indications that the driveshaft might be twisted that much?

spokejr
07-21-2017, 08:14 PM
Hey Ken,

Other than 50+ years of dirt and scuzz, that shaft looks like original. Take away the patina and it would look new.

Ken

DEEPNHOCK
07-21-2017, 08:33 PM
Dana would sometimes build driveshafts with a 'slight' offset to control/alter driveline harmonics.
But not 20 degree's... Whoaa...

WCP
07-21-2017, 08:57 PM
As I recall, I think it is more like 11 degrees on Stude driveshafts.

Dwain G.
07-21-2017, 11:17 PM
That's the way most one-piece Stude driveshafts are made. There is an old bulletin explaining that it was done to dampen out some 'disturbance'. The offset varied between about 8º and 12º depending on year and model. It's noted in the shop manual spec pages.
If you find the seam in the driveshaft tube and sight down along the seam it will be straight.

spokejr
07-22-2017, 01:22 AM
I can find in the factory manual that the length needs to be 51 29/32" length but I don't see anything in the general specifications page about being out of phase by any amount of degrees. I know some are so now I am really confused.

As for possibly twisted, not likely as the seam weld is straight.

The guy at the shop wanted to know because he is aware some cars can be very slightly off, some as much as 30 degree (69 Camaro in particular).

If anybody has a copy of the bulletin show what the amount is, please post it.

Thnaks, Ken

64Avanti
07-22-2017, 02:18 AM
Because of offsets between the transmission and rear axle in two different directions and angles between the transmission and rear axle not being ideal, the vibration can be minimized by using some angular offset different from what would be expected.