As you increase the driveshaft angle you increase the longitudinal vibration. This has nothing to do with the balance of the driveshaft, and a perfectly balanced driveshaft will experience it. It is a physical phenomenon brought on by changing the plane of a driveshaft operation(angle) using only the 4 bearing points of the u-joint. The greater the angle, the greater the longitudinal displacement. The greater the mass of the driveshaft, the greater the force from the displacement.
Standard gearing produces ~3300 RPM @ highway speed. At that RPM our max angle should be no more than ~5.5 deg. We run closer to 9 deg… At 9 deg, our max RPM should be under ~1750 RPM…
on the 4X we run a 61” rear DS. That is the maximum specified 1 piece shaft length for the type 16 DS, so we have the largest mass you are going to see in this type driveshaft. The front shaft has about the same angle, but is shorter(less mass).
the 6X has a raised pinion due to the power divider in the front axle right? Much shallower driveshaft angle and reduced longitudinal vibrations… The later A1’s with the raised rear pinion also are better configured…
This is one of the biggest benefits of eco hubs, it brings highway DS RPM down to ~ 1650 RPM And inside the max RPM at our angles… also cuts engine RPM in half at cruise…
From the dana/spicer website…
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