1slow370

it's not gear backlash it's gear noise you only have backlash between spinning faster and spinning slower like right at the top of revving the engine between rpm going up and down for maybe half of a tenth of a second. All straight cut gears sound like that at those speeds there is nothing wrong. helical gears would be quieter but they eat more power and are weaker. the noise is probably due to improper set gear mesh, bearing issues or more likely a crappy jack shaft setup which varies from application to application.

Edit: notice how the rear side pulley on the jack shaft is moving when he rev's it = bad alignment with supercharger + bad mounting the whine could be belt bind and the pulley's screaming at the guy telling him they don't like to bend. thats for the squeal as for the chattering in some of the videos THAT could be backlash from the motor speeding up and slowing down at idle. again its due to the straightcut gears and not having a backlash eliminator(sheetmetal gear, or a two piece adjustable anti-lash gear)