Mitre saw makes horrible noise

Bearing failing or debris on shaft

a bearing ,brushes or brake broke more likely the brake mechanism if blade coasts

You probably mean a Milwaukee mitre saw. McCulloch does not make a mitre saw. Go to eReplacementparts.com and enter your make and model number. If they don't have it, its probably not available anywhere. You'll have to go to a machine shop instead. Look it the yellow pages for "Machine Shop".

Does the saw make any noise? If not it could be an open circuit in the field coils

Highly unlikely the armature would warp. Both front and rear armature bearings would be my first guess.

I have just taken one to pieces for a friend with the same problem and as I suspected the drive gear is stripped of all its teeth and the the amateur worm drive isn't much better. It's a common fault on these saws, (before retiring I was a workshop manager for a major tool hire company) so I know what I'm talking about. Strip of any useful bits and recycle the rest at your local council yard. I'm going to attempt to make something out of it, don't know what yet.

Its supposed to make a noise like that...I read about the braking after trigger release

your description sounds like the gears inside the the same differential you just replaced.

This sounds like a problem with the electric brake on the motor.

check the brushes youdoit