How can I retorsion my 306 Dturbo rear axle?

What is the proceedure to remove torsion bars so as to retorsion the torsion bars.The axle is out of the car, I have removed the axle mounting brackets but cannot determine how the bars can be moved?
Is there a link where I can view an exploded view?
It is a 1999 T reg 306 dturbo.
I purchased a second hand axle which is causing the car to "crab", no matter what we have tried we cannot elliminate the "crabbing" effect.