two things you can adjust
one done off the car one done on the car
the bit that connects to the steering column is the screw or worm shaft
it has a splined end
on the screw runs the ball nut
its a nut filled with balls and it has big teeth
its big teeth are wedge shaped
across the teeth runs the sector shaft
it exits the bottom of the box and conects via the pitman arm to the cross link
it has big teeth meshed with the teeth on the ball nut.
the adjuster screw on the box
a allen headed stud with a lock nut
basically jams the teeth on the nut harder into the taper on the teeth of the sector shaft.
now you can or course undo the lock nut and wind in the allen stud further
and you will eventally make the steering tight in the middle
however this is a waste of time
if
1) its already tight in the middle
2) the screw shaft connecting to the steering column (that the toothy ballnut runs on, its got balls in it) is flaoting up and down in the case
to stop it floating up and down in the case
first back off the adjuster
then, and you will have to do this from below
the end of the box that faces the steering column has a hex shaped lock ring
its massive
hit it backwards with a wooden rod and a mallet to loosen
this unlocks the aluminium (note soft and easy broken) end of the box
you twist this to apply load to the bearings on the screw shaft.
right = tighter
idealy you'd do this off the car
and measure the restaince to turning with a 6 inch lever and spring balance
but frankly if the box has play i'd just nip it up a few mm tighter
put the lock ring back on
then
go back with the wheels off the ground
and wind box back and forth
do up the allen stud adjuster with wheels in the middle tight
check the steering wheel is stiff in the middle to turn
then back off the adjuster so its not stiff any more
if you have done all of this
you may now find that the steering pulls under power assist one way or the other, due to you aletering the postion of the inernals slightly in relation to that kinda seesaw valve that applies the assist presure
this is adjusted out by moveing the block that the power steeing pipes go into on the case
tiny smidge one way will make the steering wheel whip round to full lock one way
too much the other way makes it do the reverse
whatch ya thumbs
you have to get it just right.
dave
or
use a smaller steering wheel for MOT

they measure at the rim..
Dave