I replaced my outback clutch about this time last year with an after market clutch.  Once the engine is warm and only once it gets warm the clutch chatters when taking off from a complete stop.  It shakes the motor and the entire car.   It has done this from the day I put in the new clutch I just learned how to clutch it to prevent it from happening severly.  Not sure if this is a clutch or flywheel problem.  Any ideas?

Did you replace just the clutch disk or get a clutch kit including both bearings and a pressure plate?

Did you resurface or replace the flywheel?

Why was the clutch replaced in the first place? slipping/worn out? how many miles (just trying to get a feel for the car)

What brand of clutch did you use? 

Did it come with a snout repair sleeve for the transmission?  

 

Subaru's are especially prone to clutch chatter partly because the release bearing wears the snout of the transmission, and eventually it causes uneven engagement of the release bearing to the pressure plate, which then causes uneven engagement of the pressure plate to the clutch disc.