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Originally Posted by philofab
Driveshafts have to have the same angle on both ends to eliminate vibration. When you move the pinion left or right you are inducing the same angle on the front and rear u-joints at the same time. The factory does this all the time for gas tank, exhaust, and suspention clearance. Take a look under 70s ford vans, the center section on the rear end is offset on one side by about 8 inches. The engine and trans are not offset.
If for some reason you can't create the same angle on both U-joints you need a double cardan joint (aka CV joint) on one end to eliminate vibration. Caddilacs and Ford Broncos use these from the factory on driveshafts. Broncos use them because the driveshaft is so short the angle is extreme. Caddilacs use them because the pinion is downhill to create tunnel clearance.
I centered the housing on the rear end I just built for looks and to move the driveshaft over so I could fit a torque arm next to it in the stock tunnel. Things that aren't symetrical drive me nuts.
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This is good information. I didn't know the factories did it. When I was racing, we tried to keep the drive line as straight as possible due to parasitic losses. I had read several articles on this issue. One of the examples they gave was take a ratchet, 2 universals, and extension and a socket and put it all toegether with the ratchet as the tranny output and the socket as the pinion yoke. Then put it on a realatively tight bolt. Hold everything straight and perpendicular and loosen it. Then retighten it and loosen it again holding the ratchet offset to one side and parallel to the head of the bolt. It should feel just a bit harder to do. I tried it and have to say it is very subjective. It did however make sense to me with regard to friction and force vectors. However minute it may be it all adds up. Anyway great information as always.