If you have noises coming from your rear drive, it could be because of problems with your ring and pinion gear, drive shaft, or u-joint. If the noise becomes persistent or louder over time, it should be inspected without delay as this could be a possible safety issue.
Guzzi Ring and Pinion gears are similar to most any automotive ring and pinion set up; noises usually stem from a worn out or damaged pinion gear. Gear damage generally occurs when there is a lack of gear oil, making leaks a high concern when inspecting that area of the drive train.
When we inspect a rear drive unit, we first check the pinion gear for wear as 99% of the time its the first to go. Pinion gears that are starting to wear will first get rough areas on the base of the mating surface, this then will turn into pits, followed by small chips, and then pointed gear teeth towards the outside of the pinion. Soon gear teeth with start to break off completely, making fun noises in your rear drive unit.
We also open and inspect the ring and pinion, check the back lash of the ring and pinion gear. If necessary we will replace those worn out parts with either new or quality used components. All rear drives carry the famous Cycle Garden one year unlimited mile warranty. We also can inspect and replace the splined hub on the rear wheel, and the drive spline on the unit itself.
Another source of rear end noise can be from the u-joint or the u-joint carrier bearing. It is better to do a physical inspection, as it is difficult to troubleshoot noises over the phone. Many noises or questions can't be diagnosed without cracking them open and doing a full inspection. So if your hearing noises back there, have it checked out.