Quantcast Rack-and-Pinion Service

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WORM  BEARING  PRELOAD—Assures  that NOTE the   worm   shaft   is   held   snugly   inside   the   gearbox housing. If the worm shaft bearings are too loose, the worm shaft can move sideways and up and down during operation. OVER  CENTER  CLEARANCE—Controls  the amount  of  play  between  the  pitman  arm  shaft  gear (sector)  and  the  teeth  on  the  ball  nut.  It  is  the  most critical adjustment affecting steering wheel play. NOTE Set  the  worm  bearing  preload  first  and then the over center clearance. The  basic  procedures  for  adjusting  worm-bearing preload are as follows: Disconnect the pitman arm from the pitman arm shaft.  Loosen  the  pitman  arm  shaft  overcenter  adjusting locknut and screw out the adjusting screw a couple of turns.  Then  turn  the  steering  wheel  from  side  to  side slowly. Using a torque wrench or spring scale. measure the amount of force required to turn the steering wheel to the CENTER position. Note the reading on the torque wrench  or  the  spring  scale  and  compare  it  to  the manufacturers  specifications. If readings are out of specifications. loosen the worm-bearing locknut. Then tighten the worm bearing adjustment  nut  to  increase  the  preload.  Loosen  it  to decrease preload and turning effort. With the preload set to  specifications.  tighten  the  locknut.  Make  sure  the steering wheel turns freely from stop to stop. NOTE If the steering wheel binds or feels rough, then  the  gearbox  has  damaged  components and should be rebuilt or replaced. The basic procedures for adjusting the over center clearance are as follows: Find the CENTER position of the steering wheel. This is done by turning the steering wheel from full right to full left while counting the number of turns. Divide the  number  of  turns  by  two  to  find  the  middle.  This allows you to turn the steering wheel from full stop to the  center. Most  gearboxes  are  designed  to  have  more geartooth backlash (clearance) when turned to the right or left. A slight preload is produced in the  center  position  to  avoid  steering  wheel play during straight-ahead driving. With the steering wheel centered, loosen the over center  adjusting  screw  locknut.  Turn  the  over  center adjusting  screw  in  until  it  bottoms  lightly.  This  will remove  the  backlash. Using  the  instructions  in  the  service  manual, measure  the  amount  of  force  required  to  turn  the steering wheel. Loosen or tighten the adjustment screw to meet the manufacturer’s specifications. Tighten the locknut  and  recheck  the  gearbox  action. When adjustment fails to correct the problems, the steering gearbox needs to be overhauled or replaced. Overhauling   a   gearbox   is   done   by   disassembling, cleaning, inspecting, replacing worn components, and seals. After reassembling the gearbox. fill the housing with  the  correct  type  of  lubricant.  Most  manual steering systems use SAE 90 gear oil. Make sure that you   do   NOT   overfill   the   gearbox.   Refer   to   the manufacturer's   service   manual   for   the   particular gearbox  you  are  working  on  since  procedures, specifications, and type of lubricants vary. RACK-AND-PINION  SERVICE.—Rack- and-pinion  steering  systems  have  few  parts  that  fail. When problems do develop, they are frequently in the tie-rod ends. When NOT properly lubricated, the rack and pinion will also wear, causing problems. Depending  upon  the  manufacturer,  some rack-and-pinion  steering  systems  need  periodic lubrication. Others only need lubrication when the unit is being reassembled after being repaired. Most  rack-and-pinion  systems  have  a  rack  guide adjustment screw. This screw is adjusted when there is excessive  play  in  the  steering.  Basic  procedure  for adjusting  rack-and-pinion  steering  system  is  as follows: Loosen the locknut on the adjusting screw. Then turn the rack guide screw until it bottoms slightly. Back off  the  rack  guide  screw  the  recommended  amount (approximately   45   degrees   or   until   the   prescribed turning effort is achieved). Tighten  the  locknut.  Check  for  tight  or  loose steering and measure steering effort. Compare with the manufacturer's   specifications.   If   not   with 8-26



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