Some folks have said they didn't take them out and had no problems. It is recommended to remove them.
Which do you have clutch or cone?
Do you have the friction modifier additive in it?
If you don't that might be your issue.
Friction modifier is kind of a misnomer, it doesn't increase friction, rather it reduces it to allow the clutches/cones to slip a little under normal driving conditions to help alleviate the chatter.
