Over-Center Preload

With worm bearing preload adjusted, rotate stub shaft slowly from stop to stop while counting total number of turns. With stub shaft positioned at either stop, rotate stub shaft back 2/3 total number of turns counted. Stub shaft should be back to exact center position. Flat on stub shaft should be facing upward and parallel to side cover and master spline on pitman shaft should be aligned with adjuster screw.
Turn pitman shaft adjuster screw counterclockwise until extended, then back off one full turn. Place INCH-lb. torque wrench in vertical position on end of stub shaft. Measure gear over-center torque by rotating torque wrench attached to stub shaft in a 90 degree arc, 45 degrees on each side of center. See Fig 1 . Record highest degree of arc on each side of center. Record highest reading.
Turn adjuster screw in until torque required to rotate stub shaft is 6-10 INCH lbs. (.6-1.1 N.m) greater than reading in step 2). Continue adjustment until over-center reading is within specification. See LASH ADJUSTMENT PRELOAD table. Tighten adjuster screw lock nut when reading is obtained.

LASH ADJUSTMENT PRELOAD

Application

Over-Center INCH Lbs. (N.m)

⁽¹⁾ Total

New Gears

6-10 (0.7-1.1)

18 (2.0)

Used Gears ⁽²⁾

4-5 (.5-.6)

14 (1.6)

⁽¹⁾	Total preload is sum of worm bearing and over-center preload.

⁽²⁾	In service for more than 400 miles.

Fig 1: Adjusting Over-Center Preload

Courtesy of GENERAL MOTORS CORP.