To  measure  ring  and  pinion  backlash,  position  a dial indicator stem on one of the ring gear teeth. Then, while holding the pinion gear STATIONARY, wiggle the   ring   gear   back   and   forth.   Indicator   needle movement  will  equal  gear  backlash.  Compare  your measurements to the manufacturer’s specifications and adjust as needed. Backlash  adjustment  can  be  made  by  adjusting nuts or by moving shims from one side to the other. To increase backlash, move the ring gear away from the pinion gear. To decrease backlash, move the ring gear towards the pinion gear. RING  AND  PINION  TOOTH  CONTACT PATTERN.—The    ring    and    pinion    tooth    contact pattern   is   used   to   double-check   ring   and   pinion adjustment. To  check  the  accuracy  of  your  adjustments,  coat the ring gear teeth with a thin coat of red lead, white grease, hydrated ferric oxide (yellow oxide or iron), or Prussian blue. Turn the ring gear one way and then the other  to  rub  the  teeth  together,  producing  a  contact pattern on the teeth. Carefully note the contact pattern that shows up on the teeth where the substance used has been wiped off. A good contact pattern is one located in the center of the gear teeth (fig. 5-21). Figure 5-21 shows several ring and pinion gear contact patterns. Study each and note  the  suggested  correction  for  the  faulty  contact. Note  the  names  of  the  areas  on  the  ring  gear.  These include the following: TOE (narrow part of the gear tooth) HEEL (wide part of the gear tooth) DRIVE SIDE (convex side of the gear tooth) COAST SIDE (concave side of the gear tooth) When used gears are adjusted properly, the contact pattern will vary from that of new gears. The important thing to keep in mind with used gears is that the pattern should be closer to the toe than the heel of the tooth, as shown in figure 5-21. Notice that the ideal tooth pattern on new teeth is uniform on both sides, whereas the used gear   indicates   considerably   more   contact   on   the coasting side. Once you have obtained the proper adjustment on the ring and pinion, bolt the carrier housing in place. Make  sure  you  use  a  new  gasket.  Tighten  the  bolts according  to  the  manufacturer’s  specifications  to prevent  them  from  working  loose.  Reinstall  the  axle shafts and new gaskets. Reconnect the drive shaft and fill the axle housing with the proper lubricant. REVIEW  2  QUESTIONS Q1.   The must   be   capable   of providing  torque  to  both  axles  when  turning comers. Figure 5-21.—Tooth contact patterns. 5-22