These 2 gears have been printed in ABS to replace the original ones from the kit.
I've printed them with lot of filling (Infill solidity) to have strong gears as they are going to be very sollicited !

The print went out quite well but I must have filled it too much.
As a result, the gears are a bit bigger than the original CAD dimensions.
This might be a big problem because the distance between the 2 axes might then be too big if the original design didn't include a margin of error.
Well let's try to fix them in place. That's the only way to know. 

No... that first try is a fail.
My gears are too big so they can't fit in place (distance between axes being too big).
I decided not to print them again but to sand off the (small) excess of ABS.
It was not an easy task because of all the small teeth !
I had to be patient...

But after a few tries (I think I've tried at least 3 times before it fits, but at least I know how to change them pretty fast now) they finally fit well enough so I could give them a try.

The result is great !
The overall noise generated by the original gears has allmost completely disapeared.
And even better, I have the feeling that the final print quality has really been improved.

Conclusion : these gears are a must have ! 

Thanks Chylld !