Stage 1: First of all, locate your loco folder (for example, C:\Program Files\Steam\steamapps\common\RailWorks\Assets\Kuju\RailSimulator\RailVehicles\Diesel\Class166) then look for the audio folder after double clicking the loco folder.

2. If you want to replace a Old .dav with a new one, you'll need to open another desired Loco audio folder, (For example changing the Brake squeal noises on the Class 166 to the class 801 Brake squeal noises.) afterwards, locate your required .dav files, (example T_166_Door_open) and copy over your required dav to replace the old one with.

3. right click then left Click the original 166 door open .dav and click "Rename" this will then bring up a box on the DAV to rename your file, don't delete the original name, highlight the original by right clicking in the box, and drag the cursor to the left whilst holding right click, then press CTRL+C, then click away from the DAV, delete the original 166 door open sound and find your newly copied door open dav, left click and rename that dav, (deleting the original name of the new dav by pressing backspace, you can then press CTRL+V to copy over the old name (T_166_Door_Open) then press ente, then it should be finished