Rover V2 robot kit - twin motor gearbox

Hi,
When I have been running my rover v2 robot, the gearbox is making a very odd sound. I think there is some friction and even after rebuilding the gearbox, the sound has not gone away. I have also used grease. What do you recommend I do?
I tried to attach the video of the gearbox running so the sound could be heard, but it says ‘The extension mp4 is not allowed’. Is there any other way I could attach the video?
Thank you,
max

You can upload the video to YouTube and embed it here. Note that the gearbox is really noisy and sounds “scratchy”.
Provided it has been assembled correctly, and the gears spin freely, the noise is caused by inefficiencies in the system. We’ll watch the video just in case.
You can reduce the noise by using additional grease and covering the bottom.

I have uploaded the video. youtu.be/cYOGRWZxuPI

Thank you,
Max

That’s indeed the normal noise. Be sure to add the grease which came with the Tamiya gear box (little blue container).
Feel free to add additional grease to try to reduce the noise and you can cover the bottom however you like.
Other with sound: youtube.com/watch?v=QnsgMo-J84w