STEP TWO — INPUT DATA
Once all the relevant measurements have been collected, visit the Spicer Parts website to find its Torsional Analysis Calculator — spicerparts.com/ calculators/torsional-analysis-calculator.
The calculator uses several complex formulae to interpret your data, and provides a number of final values to interpret. The rotational speed of the driveshafts is measured in radians per second (rad/sec), and, using Steve’s measurements, gave the following results: How do we interpret these? Well, the Spicer Parts calculator tells us how to do that.
Inertia effects — Maximum 1000rad/sec/sec Inertia effects (driving member) — usually caused by a large operating angle at drive end of driveshaft. Inertia effects (driven member) — usually caused by a large operating angle at driven end of driveshaft. Torsional effects — Maximum 300rad/sec/sec Usually caused by large, unequal operating angles, or out-of-phase driveshafts. As such, we can see that the torsional effects are the most likely cause of Steve’s driveline vibration.
This can, in theory, be remedied by evening out the driveline angles. The inertia effects at the driven member (diff) are also higher than ideal, which can be remedied by altering the diffpinion angle, to reduce the angle between it and the rear driveshaft.
Adjusting the centre bearing height can help to reduce the negative effects of excessive inertia or torsional effects on the driveline -0.5° -2.3° -1.7° -3.1°