Jack up the hub by the amount you wish to lower the ride height. The new measurement will be the figure you wrote on the tape, minus 5mm, minus the lowering amount. i.e. if you're original figure was 420mm & you want to lower by 25mm, the new figure will be 390mm.
Re-insert the torsion bar. If it doesn't slide in first time (it probably won't), rotate the bar & try again. Eventually you will find a position where both ends of the bar will just push in. If you left the slide hammer in the end, it'll be easy to do this on your own, otherwise you'll need someone under the car aligning the other end of the bar with the fixed bracket.
Remove the slide hammer.
Now do the same for the other side of the car.
When that's done, temporarily refit the wheels & lower the car to the ground to check the height. Bounce the car a couple of times to allow it to settle.
If all's ok & you're happy with the ride height, get the car back on the axle stands & remove the wheels.
Refit the offset washer & tap it into position, aligning the hole with the torsion bar.
Before fitting the countersunk screw, refit the slide hammer through the washer & pull the torsion bar hard up against the washer. Then, remove the slide hammer & fit the screw.
Check the clearance between the trailing arm & it's bearing seal & adjust it to 0.5mm using feeler gauges, tapping the arm in or out with a mallet.
At the other end of the torsion bar, turn the screw anti-clockwise until it just stops against the end cap. Refit & tighten the nut & washer, then re-check the trailing arm/seal clearance.
Re-attach the bottom shock mountings. You may need to jack up the hubs slightly to get the bolt holes to line up.
Refit the torsion bar at one end & loosely fit the hexagon headed fixing screw. From the other end, push the other plate on the end as far as it will go. Screw in an M8 screw with a nut & washer on, through the plate, into the anti-roll bar & tighten the nut to draw the plate onto the bar until there is 1mm between the plate & the trailing arm.
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