Bought a set of avid juicy seven ultimate brakes,i squeezed the brake lever and now the pads are shut tight how do i slacken them off again!

If you already overhauled the caliper, I would overhaul the lever as well. In fact, I usually overhaul the entire system instead of one or the other. As for the chattering sound, it sounds like the rotor is catching the edge of one of the brake pads. Check to see if the pads are retracting fully or see if the pads are loose in the caliper.

I am assuming you are looking for the clamp portion of the brake lever.

If you do a google search for the following you can find several options on-line, or go into your local bike shop and have them order for you, they may even have in stock if they do alot of work with Hydraulic brakes.

Search: Avid Juicy Brake Lever Clamp or Avid Hydraulic lever clamp.

Here is a link as an example of a result.

It sounds like you have a piston that is not fully returned and is sticking.

Get a big flat bladed screw driver, take the wheel out and very carefully insert the screw driver into where the disc would sit and use the screw driver to try and push each brake pad back in without damaging your brake pads.

If this works go to a local bike shop and ask them for a avid brake insert for transporting your bike so this does not happen in future! :)

It is a lose bolt somewhere, OR somebody has touched your rotor with their hands OR there is oil in the pads.

Check ALL your bolts for correct torque, buy new pads and Rubbing Alcohol and install them AFTER you clean off the rotor and your hands with the Rubbing Alcohol. TRY not to touch the rotor or the pads with your hands.

They do drag by default ... mostly ...a little bit ... that is why they dont sit square with the rotor but rather a few degrees to the right or left.

Juicy's are prone to sticky pistons.REMOVE pads,clean calliper ,pull lever lightly and add a drop of hydraulic fluid to the edges of the pistons to lube.Recess pistons,wipe off excess fluid and fit pads.If this doesn't work they might need bled.

Your brake failed and you need to take it to a good bicycle repair shop in your area. Hydraulic brakes on bicycles are not easy to self service as you need specialized tools and the proper replacement parts.

use a flat screw driver and push the pads back in on the calliper. Be gentile though.

The brake disc may be warped from excessive heating. This may be caused by a dragging brake pad. the disc may have been bent from an impact.
This can also be caused by the pins holding the brake caliper being stuck. Try some WD40 on them and tap them (gently) to free them.

Your brakes adjust automatically (so when the pads wear down your levers don't get looser). What you did was pull the brake lever and it adjusted making the pads shut.

Anyway all you need to do is take a wide flat-head screw driver and wiggle it back and forth between the 2 pads.