If you have the "notch" then you are adjusted just a little too tight already.

The sector on the output shaft gets closer to the worm as it turns past the middle and the adjustment screw moves the sector up and down which, in turn, moves the center line of the sector closer or farther from the center line of the worm. As it is curved, that increases or decreases the lash (distance) between the two to make up for wear.

There are actually two adjustments on the box. The second one is for the end-play on the worm (on the input shaft... attached to the coupler and your wheel). It is adjusted by adding or removing shims from the end cover. It is checked by removing the box and measuring the torque required to turn the input shaft when the output shaft is removed. Of course, I just do it the same way I do for wheel bearings... not loose, not tight.

I suggest you loosen the adjuster just a little (1/8 turn or less) and see if that helps. If the steering feels excesively loose or you have more "shimmy" introduced at the wheel, then adjusting the worm lash may help (followed by readjusting the screw on the sector gear).

Of course, if you are that far into it you ought to rebuild it.

Wear items beyond the ball-bearings include: Oil seals (2), Output shaft cover (unlikely unless hideously abused), plain bearings (bushes) on output shaft (2), worm gear, sector gear (rather permanently attached to output shaft.. at least as far as the shadetree mechanic is concerned).

ON a side note, if the "notch" is not at dead center, your steering box is not centered OR the steering wheel is not centered. The "off-center" could be at the steering wheel, coupler or output shaft.

Make certain the box is full of nice clean gear oil.

Mike!