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Home >> Mercury >> 1981 >> Capri Turbo RS >> Repair and Diagnosis >> Drivelines & Axles >> Differentials & Drive Axles >> Drive Axles - Ford Motor Co. - 7 1/2" & 8 1/2" Ring Gear >> Overhaul >> Adjustment >> Differential Bearing Preload

Differential Bearing Preload

  1. Apply thin coating of axle lubricant to bearing bores. Place bearing cups over side bearings and place differential case in housing. Install a 0.200" gauge disc spacer on ring gear side (left) of case between bearing cup and case. Install a 0.300" gauge disc spacer on pinion gear side (right) of case between bearing and case. Install bearing caps in original positions and tighten bolts to 30 INCH lbs.
  2. Install adjuster rod (T78P-4136-A) into ring gear side (left) of axle tube and retain in position with existing brake backing plate bolts and nuts. Tighten adjuster rod nut to 40 INCH lbs. to move differential case to right side of housing. Rotate differential case several times to seat bearings and recheck adjuster rod nut torque (maintain 40 INCH lbs.).
  3. Using a feeler gauge, select thickest blade that will enter between gauge disc and carrier bore on ring gear side of case. Feeler gauge should fit with slight drag. Remove and record feeler gauge thickness. Then add 0.500" to recorded feeler gauge thickness for total shim thickness. See Fig 1.
    Fig 1: Measuring for Side Bearing Shim Thickness
    G09330615Courtesy of FORD MOTOR CO.
  4. Release adjuster rod enough to remove 0.300" gauge. Remove right bearing cap and gauge. Install bearing preload spacer (T78-4135-B for 7 1/2" ring gear; T79P-4135-A1 for 8 1/2" ring gear) between bearing cup and carrier bore with rubber "O" ring facing outboard. Reinstall bearing cap and tighten to 30 INCH lbs.
  5. Rock ring gear back and forth, while tightening adjuster rod until zero backlash is obtained. Using a feeler gauge, repeat step  3). Add 0.200" to feeler gauge thickness.
  6. Left shim thickness is total thickness recorded in step  5) MINUS 0.008". Right shim thickness is total shim thickness obtained in step  3) MINUS total obtained in step  5) PLUS 0.016". See Sample Calculation .
    NOTE: Side bearing shims are available in various thicknesses. If shim size required is not listed, round DOWN to nearest size available.
    SAMPLE CALCULATION

    Feeler Gauge Reading (Step 5) .086"
    PLUS Spacer Thickness .200"
    Total .286"
    MINUS .008"
    EQUALS LEFT Shim Thickness .278"
    Feeler Gauge Reading (Step 3) .040"
    PLUS Spacer Thickness .500"
    Total .540"
    MINUS Total (Step 5) .286"
    EQUALS .254"
    PLUS Preload Constant .016"
    EQUALS RIGHT Shim Thickness .270"
  7. Remove adjuster tool from axle housing. Remove bearing caps, disc spacer and preload spacer from carrier housing. Install carrier spreader and dial indicator. Spread carrier housing 0.016" (measured at top of housing). Remove dial indicator. Install left shim, push differential case and bearing cap to left and install right shim (tapping with plastic hammer if required). Release spreader and remove from housing.
    NOTE: Do not exceed differential case spread of 0.016".
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