It's been my experience that if you have a marginal driveline angle issue that coasting in neutral will change the pitch/noise/sensation.
Let's say you have a pinion angle that is too high. It will generate noise and chatter on accel, but quieten down on decel.
Adversely, if the pinion angle is too low, it will tend to be fine under acceleration but growl under coast as the pinion angle naturally drops a few degrees.
Of course anything leaf sprung will react more so than something linked will.
