Just installed new toilet refill valve. Everything seems to be working fine except for a loud whining sound when it flushes. Any ideas on how to stop this! Thanks!

Which type of valve is in the toilet?

Fluid master fill valve

It stops once the floater reaches the top.

400A Fill valve

Turn off water at the stop valve under the tank.

Remove tank lid and place it some where that it can't get broken.

Flush toilet. Reach in under float, lift float and grasp shank.
(The float lever must be in the up position).
Press down and turn the cap counter clockwise and remove it.

Place a small cup or hold your hand over the top of the fill valve and briefly turn on the water to flush out the valve.
Make sure the seal in the valve cap is properly installed.
Reinstall the cap and turn on the water.

Not the best video but he does how you how to remove the cap. (Doesn't need to try to be so dramatic).

https://www.youtube.com/watch?v=WYWIOiGWFYY

Hello Kristin,

Follow Herald instructions you may be able to resolve your issue, the video is not that great see the attach images may help you, good luck.

John