Model 28-IFS
TOTAL DIFFERENTIAL CASE ENDPLAY INSPECTION1. Attach ring gear to differential case using new bolts, then tighten bolts alternately and evenly to 70-90 ft lb.
2. Clean trunnions on differential and install bearings onto differential case. Remove all burrs and nicks from hubs so bearings rotate freely.
Fig. 6 Total Differential Case Endplay Inspection:
3. Place differential case into carrier (without pinion). Differential case should move freely in carrier assembly. Position a suitable dial indicator against differential case flanges. Locate tip of indicator on flat surface of one ring gear bolt. Force differential case toward dial indicator as far as possible and zero dial indicator with force still applied. Dial indicator should have a minimum of 0.350 inch travel. Force differential case away from dial indicator as far as it will go. Repeat this procedure until same reading is obtained. Record dial indicator reading as measurement "A" on a work sheet for calculating ring gear backlash and differential bearing preload shims. This reading indicates amount of shims needed behind differential side bearings to take up total clearance between differential bearing cup and carrier. This reading will be used during "Pinion & Ring Gear Backlash Inspection".
4. Remove differential case from carrier. Do not remove differential case bearings at this time.
DRIVE PINION INSTALLATION
Two separate adjustments affect drive pinion and ring gear tooth contact: pinion depth and pinion to ring gear backlash.
Fig. 7 Drive Pinion Installation.:
Pinion depth is controlled by a selective thickness oil slinger located between drive pinion head and inner pinion bearing cone and an oil baffle located between inner bearing cup and carrier bore.
Pinion to ring gear backlash is controlled by preload shims located between the differential bearing cup and carrier.
During pinion depth adjustment, the size of the selected thickness of oil slinger and baffle controls pinion position. Increasing oil slinger thickness moves pinion toward ring gear (-). Decreasing oil slinger thickness moves pinion away from ring gear (+).
Fig. 8 Ring & Pinion Identification:
On the button of each drive pinion is marked a plus (+), a minus (-) or a zero (0). These markings indicate the position for each gear set. The position is determined by thickness of baffle between inner pinion bearing cup and carrier bearing bore and thickness of selective oil slinger between pinion head and inner pinion bearing. Any pinion depth change is made by changing thickness of selective oil slinger.
If the original gear set is being reused, measure original baffle and selective slinger and replace with exact same size, if necessary.
Fig. 10 Drive Pinion Adjusting Shim Thickness Chart (Metric):
If a new gear set is being used, notice the plus (+), minus (-) or zero (0) etchings on both original and new drive pinion and adjust thickness of new selective oil slinger according to charts.
DEPTH GAUGE INSPECTION
Fig. 11 Depth Gauge Tool Selection.:
Fig. 12 Depth gauge Tool Selection.:
1. Refer to charts for correct tool on particular axle assemblies. If any gauge surfaces become nicked, high spots must be removed with a medium India oilstone to ensure no erroneous readings are obtained.
2. Install oil baffle into inner bearing cup bore in carrier.
Fig. 13 Inner & Outer Pinion Cup Installation Tools:
3. Install inner and outer pinion cups using suitable tools. Prior to installing pinion bearing cups into aluminum or magnesium housings, apply graphite lubricant part No. A-1040-CR, or equivalent, to bearing cup bore to prevent metal particles from being picked up as cup is pressed into bore.
4. Place a new inner pinion bearing over proper aligning adapter and insert into pinion bearing retainer assembly. Place outer pinion bearing into bearing cup in carrier and assemble handle onto screw and hand tighten. Note 3/8 inch square drive in handle is to be used to obtain proper pinion bearing preload.
5. Center proper gauge tube into differential bearing bore, install bearing caps and tighten to 30-45 ft lb. To preload bearings, torque handle to 15-35 inch lb.
6. Using suitable feeler gauges, select thickest feeler gauge that will fit between gauge tube and gauge block. Insert feeler gauge directly along gauge block to ensure a correct reading. Feeler gauge should fit between gauge tube and gauge block with only slight drag.
7. After correct feeler gauge feel is obtained, obtain oil slinger of same thickness as feeler gauge, provided new pinion gear is marked with a zero (0). If new pinion gear is marked with a plus (+) reading, the plus (+) amount stamped on pinion gear must be subtracted from thickness dimension obtained in preceding step. If new pinion gear is marked with a minus (-) reading, the minus (-) amount stamped on pinion gear must be added to thickness dimension obtained in preceding step. Also, exact new inner pinion bearing that was used to obtain this dimension must be used.
Fig. 14 Bearing Installation On Drive Pinion:
8. Measure oil slinger with a micrometer to verify size, then place oil slinger onto pinion and press bearing on.
9. Lubricate ends of outer pinion bearing rollers with a suitable high-temperature lubricant.
DRIVE PINION PRELOAD INSPECTION
1. Install pinion into carrier, then install a new collapsible spacer.
2. Install outer pinion bearing and thrust washer or oil slinger.
3. Coat drive pinion oil seal with suitable hypoid gear lubricant or equivalent, then install drive pinion oil seal using suitable oil seal replacer. After installation, ensure garter spring did not pop out. If garter spring pops out, remove and replace seal.
4. On Model 28-IFS axle, proceed as follows:
a. Install yoke using companion flange replacer tool No. T83T-4851-A, or equivalent, then install washer and nut. Torque to 175 ft lb.
b. Place an inch pound torque wrench on pinion nut and check pinion rotational tightening. Rotational torque should be 15-35 inch lb.
c. If reading is less than 15 inch lb, tighten pinion nut in small increments until rotational tightening specification is obtained. Do not torque nut to more than 275 ft lb, or collapsible spacer will be compressed too far.
d. If reading is greater than 35 inch lb, collapsible spacer has been compressed too far and must be removed and replaced with a new spacer.
PINION & RING GEAR BACKLASH INSPECTION
1. Install ring gear to differential case using new bolts, then tighten bolts alternately and evenly to 70-90 ft lb.
2. Place differential case into position in carrier (differential case bearings should still be installed).
Fig. 15 Ring Gear & Pinion Backlash Inspection:
3. Force differential case away from drive pinion gear, until it is completely seated against cross bore face of carrier. Position a dial indicator so indicator tip rests on a ring gear bolt head. Zero dial indicator.
4. Force ring gear against pinion gear. Rock ring gear slightly to ensure gear teeth are in contact, then force ring gear away from pinion gear, ensuring dial indicator returns to zero. Repeat this procedure until dial indicator reading is the same. This reading should be recorded as measurement "B" and reveals amount of shims necessary between differential case and differential bearing on ring gear side.
5. On Model 28-IFS axle, proceed as follows:
a. Assemble shim pack for ring gear side to measurement "B" minus (-) 0.006 inch for backlash.
b. Subtract measurement "B" from measurement "A" obtained in "Total Differential Case Endplay Inspection" procedure in this section to obtain measurement "C." Measurement "C" equals amount of shims required between differential case and bearing on side opposite of ring gear.
c. Assemble shim pack for side opposite of ring gear to measurement "C" plus (+) 0.003 inch for additional preload.
6. Remove differential case from carrier, then the bearings from case.
7. Place required amount of shims on hub of ring gear side of differential case, then install bearing and drive bearing onto hub using a suitable differential side bearing replacer.
8. Place required amount of shims on hub of differential case opposite of ring gear side, then install bearing. Place a suitable step plate on ring gear side bearing to protect bearing, then drive bearing opposite of ring gear side onto hub using differential side bearing replacer.
9. Install differential bearing cups onto bearings.
10. Mount spreader tool No. 4000-E and tool No. T80T-4000-B, or equivalents, onto carrier assembly.
11. Position a dial indicator onto carrier, then spread housing.
NOTE: Do not spread housing more than 0.010 inch.
12. Install differential case into carrier. If necessary, use a rawhide or plastic hammer to seat case in carrier bore. With partial and non-hunting/partial ring gear and pinion sets, align marks on ring gear and drive pinion, if applicable. Use care not to nick teeth of ring gear or pinion.
13. Remove spreader and dial indicator.
14. Install bearing caps and bolts, ensuring letters or numbers stamped on caps correspond in both position and direction with letters or numbers stamped into carrier, then tighten bolts to 30-45 ft lb.
Fig. 15 Ring Gear & Pinion Backlash Inspection:
15. Install dial indicator on case.
16. Check ring gear and pinion backlash at three equally spaced points on ring gear. Backlash tolerance is 0.005-0.008 inch and cannot vary more than 0.003 inch between the three points.
17. If backlash is high, ring gear must be moved closer to pinion by increasing thickness of shims on ring gear side and decreasing shims on opposite side by an equal amount.
18. If backlash is low, ring gear must be moved away from pinion by decreasing thickness of shims on ring gear side and increasing shims on opposite side by an equal amount.
19. On Model 28-IFS proceed as follows:
a. Install right hand slip yoke and stub shaft.
b. Apply a continuous bead of RTV silicone sealant 1/8 to 1/4 inch high and 1/4 to 1/2 inch wide on mating surfaces of carrier mounting face support arm, then mount carrier assembly to left hand axle arm using two guide pins. Install mounting bolts and tighten to 35-53 ft lb. Tighten one bolt and then tighten bolt directly opposite it. Tighten remaining bolts in either a clockwise or counterclockwise pattern.
20. Allow sealant one hour cure time prior to filling carrier with proper amount of specified lubricant.