Sometimes after normal usage wear & tear, a 40E can begin to make more audible noise during operations.
If production is not impacted, the noise is likely nothing to be concerned with and may dissipate over time with more usage. Many times, taking apart and re-greasing the drive with grizzly grease can help if something is catching and causing the noise.
Use the below guides as help to disassemble. Fully re-grease the drive and reassemble. If you are using grizzly grease, take care to keep it contained to the drive as it could damage the pump itself and/or membrane. Refer to https://katadyngroup.ladesk.com/884379-Types-of-Lubricant--Functions for details on when to use which type of lubricant.
Depending on your system model, refer to your owner's manual for instructions on drive maintenance as well as instructions on how to disassemble the user serviceable parts.
40E: Disassembly Page 20, Drive Maintenance Pages 26-27
80E: Disassembly Page 18, Drive Maintenance Pages 24-35