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Rear axle assembly is semi-floating, hypoid gear type with centerline of pinion set below centerline of ring gear. Axle shafts have integral wheel hubs and are supported in the differential case by side gears and in the axle housing by ball bearings. Service of these assemblies, with exception of axle housing, may be performed without removing complete rear axle assembly from vehicle.

The semi-floating, hypoid gear type rear axle assembly with separate housing is used on all Fiat models, The axle ration is 4.3-1.

Removal - 1) Raise vehicle and remove rear wheels and disc brake front shield. Remove caliper support bracket mounting bolt and remove caliper (without disconnecting brake lines). Remove bolts attaching brake disct to axle shaft hub and remove brake disc and plate.

2) Remove snap ring securing bearing dust shield. Attach slide hammer and withdraw axle shaft assembly. Inspect axle shaft bearing, dust shield and bearing retaining collar for wear or damage and replace as necessary.

Disassembly - Using suitable arbor press (A. 74108/1/2), press bearing retaining collar off axle shaft and discard collar. NOTE - Retaining collar must never be reused; replace with new collar. Remove snap ring, dust shield and bearing. If axle shaft is score or damaged, replace shaft.

Reassembly - 1) Install snap ring, dust shield and bearing onto axle shaft held vertically on solid plate of arbor press (A. 74107/1). Insert new collar into suitable holder (A. 74107/4), place in oven and heat to 571°±18°F (300°±10°C). Remove unit from oven and plae on axle shaft. Press axle shaft into collar using 13,000 lb (6,000 kg) maximum pressure.

Removal - Drain fluid, raise vehicle, and remove wheels. Withdraw axle shafts for enough to disengage from side gears. Disconnect propeller shaft, support differential and remove attaching bolts. Remove differential assembly from axle housing.

Installation - Thoroughly clean oil residue from axle housing. Position new gasket in place and reverse removal procedure.

Disassembly - 1) With differential secured in suitable holding fixture, remove two bolts and spring washers from caps and remove lock plates. Remove bolts and spring washers securing case bearing caps, and remove caps, adjuster rings and roller bearing cups. Remove differential case from carrier.

2) Turn differential carrier upside down and lock bevel pinion in place. Loosen self-locking nut securing sleeve to bevel pinion shaft and remove sleeve. Remove pinion, thrust ring, rear roller bearing cone and collapsible spacer from inside housing. Remove oil seal, oil slinger, and front bearing cone from carrier.

3) Slide collapsible spacer off pinion, then draw off rear roller bearing .Thrust washer can then be removed from pinion. Using a suitable puller, remove differential case roller bearings. Remove screws holding ring gear to differential case roller bearings. Remove screws holding ring gear to differential case then use drift to remove pinion gear from case. Remove pinion gears, side gears, and thrust washers.

FIG 3. CHECKING FOR CORRECT THICKNESS OF WASHER FOR DRIVE PINION DEPTH ADJUSTMENT

Case Assembly - 1) Install thrust washers on differential side gears and position gears in differential case. Insert pinion gears in case and engage them with side gears. Align holes in pinion gears through openings in case and insert pinion shaft. Check axial play in each side gear.

2) Axial play should not exceed .004" (.10 mm). If play exceeds specification, replace side gear thrust washers. These washers are available in various thicknesses. If correct clearance cannot be obtained, gears must be replaced. Assemble ring gear to differential case and torque to specification. Using suitable driver (A. 70152), install both roller bearings on differential case.

Drive Pinion Depth - 1) Fit front and rear roller bearing cups of bevel pinion in position using suitable driver. Using same driver, attach cone  of rear roller bearing to dummy pinion (A. 70184) then position dummy pinion in differential carrier.

FIG. 4 LOCATION OF STAMPED NUMBER ON DRIVE PINION GEAR

2) Install cone on front roller bearing and place nut on dummy pinion. Turn pinion to seat bearing cones and tighten nut.

3) Zero dial indicator (A. 95690) on a surface plate then attach to dummy pinion. Position dial indicator to allow plunger to contact roller bearing seat in differential case. Obtain minimum reading on dial indicator by moving plunger from right to left. Record reading and repeat procedure on opposite side.

4) Determine on average from the two readings, then from this average, subtract the value stamped on bevel pinion to be used. This will give correct thickness of thrust washers to be inserted between the head of the pinion and the shoulder of rear roller bearing.

5) If the number stamped on the pinion is preceded by a plus sign, the thickness of the washer to be used is derived by subtracting this number from the dial gauge reading. If the number stamped on the pinion is preceded by a minus sign, the thickness of the washer is obtained by adding this figure to the dial gauge reading.

FIG. 5 CHECKING DIFFERENTIAL BEARING AND RING GEAR BACKLASH

6) Place thrust washer (correct thickness) on bevel pinion, then rear roller bearing cone followed by collapsible spacer. Install pinion assembly in carrier and attach the front roller bearing cone, oil slinger, oil seal, and "U" joint sleeve. Install washer and self-locking nut on tail of pinion.

Pinion Bearing Preload - Secure pinion to keep it from turning. Gradually tighten nut on tail of pinion shat to 87-166 ft. lbs. (12-23 mkg). Check turning torque of pinion shaft using dynamometer (A.95697) and adapter (A. 55075) fitted to pinion nut and set to 17 INCH lbs. (20 cmkg). If turning torque is less than 14 INCH lbs. (16 cmkg), pinion nut must be tightened (without exceeding maximum torque). If turning torque is more than 17 INCH lbs. (20 cmkg), pinion must be removed an collapsible spacer changed.

Backlash and Side Bearing Preload - 1) Place differential side bearing cups on side bearings and place differential assembly into carrier. Fit two bearing retaining and adjusting rings, install caps and torque to specifications.

2) Attach suitable tool (A. 95688)  (see illustration), to differential carrier. Adjust backlash between ring gear and pinion to .0031-.0051" (0.08-0.13 mm). Insure that bearings are not preloaded.

3) Set preload by tightening two bearing adjusting rings alternately with equal number of turns until dial indicator "A" (see illustration), shows an increase of .0055-.0071" (0.14-0.18 mm). After preload is set, check backlash of bevel gears.

4) To check backlash, set dial indicator to "B" (see illustration), so that plunger rests against tooth of bevel gear. Rotate gear to obtain maximum reading. Backlash must be .0031-.0051" (0.08-0.13 mm).

Final Inspection and Assembly - With pinion bearing and ring gear backlash properly adjusted, make a tooth contact pattern check. NOTE - Check gear tooth contact using paint impression method described at beginning of this section. When pattern is satisfactory, install axle shafts, brake drums, wheels and tires, propeller shaft and refill with suitable gear lubricant.

Axle housing is banjo type with removable differential carrier and semi-floating axle shafts. Ring and pinion are hypoid type in which centerline of pinion is set below centerline of ring gear. Differential case may be either two pinion or four pinion design. The axle shafts are retained in housing by ball bearings and bearing retainers at axle housing outer ends.

All Mazda models use one basic type of rear axle assembly. Any differences in Removal and Installation or Overhaul procedures will be noted where they occur. To determine axle ratio, divide number of ring gear teeth by number of pinion teeth.

Removal (All. Exc. Pick-Up) - Remove wheel and tire assembly and brake drum. Remove brake shoe return springs and brake shoes. On RX-4 models, remove center cap adapter from axle shaft flange. On all models, withdraw nuts attaching retainer and backing plate to axle housing, then use a suitable puller (49 0259 631 and 49 0223 630A) to remove axle from housing.

Bearing Replacement (All Exc. Pick-Up) - Remove axle bearing and collar using a press and a suitable bearing adapter (49 0259 745). NOTE - If pressure necessary to remove bearing exceeds 10 tons, or if bearing adapter is not available, grind bearing retaining collar down and cut with a chisel to remove. To reassemble, apply a light coat of oil to axle shaft and place bearing retainer and spacer on shaft. Position bearing on shaft with sealed side toward axle shaft flange, then press bearing on shaft until spacer contacts shaft shoulder. Next, press bearing retaining collar on shaft until it seats firmly against bearing. NOTE - Do not press bearing and collar on shaft at the same time. In addition, if collar is installed with less than 3 tons of pressure, replace a new part.

AXLE SHAFT ASSEMBLY (EXCEPT PICK-UP)

Installation (All Exc. Pick-Up - 1) Apply a light coat of grease to oil seal in axle housing. Check axle shaft end clearance as follows. Install backing plate and gasket temporarily and measure depth of bearing seat in axle housing. Then measure width of axle bearing outer race. The difference between the two measurements indicates the required thickness of shim.

2) Shims are available in thicknesses of .004" (.1 mm) and .016" (.4 mm). After selecting correct shim pack, apply sealant to shims and position brake backing plate and shims on axle housing. Install axle shaft assembly in housing using a new gasket, then install and tighten retainer bolts. At this time, recheck end play, maximum end play allowable is .004" (.1 mm). Install brake shoes, return springs, brake drum and wheel and tire assembly.

AXLE SHAFT ASSEMBLY (B1600 & RE PICK-UP)

Removal (B1600 and Pick-Up) - Remove wheel and tire assembly, then remove brake drum and brake shoes. Remove parking brake cable retainer and disconnect brake lines at wheel cylinders. Remove nuts attaching backing plate and bearing housing to axle housing, then pull axle shaft, backing plate, bearing housing assembly, and shims off axle housng.

Bearing Replacement (B1600 and RE Pick-Up) - Straighten tools of lock washer, and using a suitable spanner wrench (49 0603 621A), remove lock nut and lock washer. Using a puller withdraw bearing and housing assembly from axle shaft, then remove backing plate. Remove bearing and oil seal from housing. To reassemble, reverse disassembly procedure.

Installation (B1600 and RE Pick-Up) 1) Install axle shaft, backing plate, and bearing housing to rear axle housing, temporarily attaching with two bolts and nuts. Mount a dial indicator on backing plate and check axle shaft end play. End play should be .002-.006" (.05-.15 mm).

2) NOTE - If both axle shafts were removed, a special procedure must be followed: The end play for the first axle shaft installed should be set to .026-.033" (.65-.85 mm). The second axle shaft installed should be set to the normal end play of .002-.006" (.05-.15 mm).

Removal and Installation - Raise vehicle until rear wheels are clear of ground. Remove drain plug and drain rear axle lubricant, reinstall plug and tighten. Remove axle shafts. Mark propeller shaft and pinion flange for reassembly reference, then disconnect propeller shaft. Remove carrier attaching nuts and withdraw carrier from axle housing. To install, reverse removal procedure, making sure to refill axle with lubricant.

MEASURING PINION HEIGHT

1) Mount carrier in a suitable repair stand. Attach a dial indicator to carrier (with button of indicator contacting backface of ring gear) and check ring gear deflection. Maximum allowable deflection is .004" (.1 mm); replace ring and pinion if above specification. Punch identification marks on side bearing supports of carrier, differential bearing caps, and side bearing adjusters. Remove adjuster lock plates, loosen bearing cap attaching nuts or bolts, and slightly back off adjusters to relieve preload.
2) Remove bearing caps and adjusters, then withdraw differential assembly from carrier, making sure side bearing races remain with their respective bearings. If necessary for replacement, use a suitable puller and remove side bearings from gear case. Straighten lock tabs, remove ring gear attaching bolts, and separate ring gear from gear case.
3) On all models except RX-4, drive out differential pinion shaft lock pin with a punch and remove pinion shaft. Rotate pinion gears 90 degrees and remove gears, thrust washers, thrust block (if equipped), and differential side gears. On RX-4 models, remove bolts joining differential case halves and separate case. Remove side gears, thrust washers, pinion gears, and spider.
4) On all models, remove pinion nut and pinion flange. Remove drive pinion and rear bearing assembly, adjusting shims (if equipped), spacer and bearing collar if used). NOTE - It may be necessary to top end of pinion with soft hammer to remove from carrier. Remove front oil seal and withdraw front pinion bearing. Using a press, remove rear bearing from drive pinion, then lift off pinion adjusting shim. If necessary for replacement, use a drift punch and remove pinion bearing races from carrier.

MAZDA REAR AXLE ASSEMBLY

REASSEMBLY AND ADJUSTMENT
Drive Pinion Depth - 1) NOTE -The use of a suitable dial indicator assembly (49 0727 570) and pinion gauging set (49 0305 555, all exc. pick-up; or 49 0603 555A, B1600 and RE pick-up) is required for this procedure. Install dial indicator on gauge body, place gauge body on a surface plate, and preload indicator .040-.120" (1-3 mm). When preloaded, turn outer ring of indicator assembly to "zero" gauge.
2) Make sure differential bearing bores are free of dirt and burrs, then install drive pinion, dummy bearing, and original pinion depth shim into carrier. Place gauge block on pinion and position indicator assembly on block so button of indicator contacts lowest portion of differential bore.
3) Record the amount indicator moves in a "+" (plus) or "-" (minus) direction from zero. Remove gauging assembly and pinion from carrier. Check rear face of pinion for the machining correction figure. If pinion is marked "+" (plus), SUBTRACT amount specified on pinion from dial indicator reading; if marked "-" (minus), ADD amount to indicator reading. NOTE - Figures on pinion are hundredth millimeters.
4) Place dummy pinion and rear pinion bearing on surface plate and compare heights. If pinion bearings is higher than dummy bearing, SUBTRACT difference from dial indicator reading, if pinion bearing is lower than dummy bearing, ADD amount to indicator reading.
5) Select correct pinion depth adjusting shim to be used for reassembly by adding or subtracting the amount determined in steps 2), 3), and 4) from the thickness of the original pinion depth shim used during gauging process. Position correct shim on pinion and install pinion bearing. Shims are available in the following thicknesses for all models except RX-4:
Identification Mark                              Thickness In. (mm)
08.......................................................   .121 (3.08)
11.......................................................   .122 (3.11)
14.......................................................   .124 (3.14)
17.......................................................   .125 (3.17)
20.......................................................   .126 (3.20)
23.......................................................   .127 (3.23)
26.......................................................   .128 (3.26)
29.......................................................   .130 (3.29)
32.......................................................   .131 (3.32)
35.......................................................   .132 (3.35)
38.......................................................   .133 (3.38)
41.......................................................   .134 (3.41)
44.......................................................   .135 (3.44)

SOLID BEARING PRELOAD SPACER AND SHIMS

47.......................................................   .137 (3.47)
For RX-4 models, the following thickness shims are available
Identification Mark                             Thickness In. (mm)
52.......................................................   .139 (3.52)
55.......................................................   .140 (3.55)
58.......................................................   .141 (3.58)
61.......................................................   .142 (3.61)
64.......................................................   .143 (3.64)
67.......................................................   .145 (3.67)
70.......................................................   .146 (3.70)
73.......................................................   .147 (3.73)
Pinion Bearing Preload (W/ Solid Bearing Spacer) - 1) Position drive pinion and rear bearing assembly into carrier, then install bearing spacer and preload shims onto pinion. Install front pinion bearing and pinion flange (do not install oil seal at this time). Install pinion nut and tighten to 110 ft. lbs. (15 mkg) on 1200 models or 130 ft. lbs. (18 mkg) on R-100 models.
2) Using a torque wrench installed on pinion nut, measure turning torque of drive pinion through at least one full revolution. If preload is greater than specified (see Axle Assembly Specifications), a thicker shim or longer bearing spacer is required; if preload is less than specified, a thinner shim or shorter bearing spacer is required. Shims and spacer are available in the following thicknesses and lengths:
Identification Mark                               Thickness/Length In. (mm)

INSTALLING COLLAPSIBLE BEARING SPACER

Shims
   4.....................................................   .013 (.34)
   6.....................................................   .014 (.36)
   8.....................................................   .015 (.38)
Spacer (1200 Model Only)
   10...................................................   1.658 (41.10)
   18...................................................   1.661 (41.18)
   26...................................................   1.664 (41.26)
   34...................................................   1.668 (41.34)
Spacer (R-100 Model Only)
   60...................................................   2.149 (54.60)
   68...................................................   2.152 (54.68)
   76...................................................   2.155 (54.76)
   84...................................................   2.159 (54.84)

INSTALLING PINION SHAFT & LOCK PIN

3) After obtaining correct preload shim pack, remove pinion flange, install pinion oil seal, and reinstall pinion oil seal, and reinstall pinion flange. Tighten pinion nut to specification.
Pinion Bearing Preload (W/Collapsible Bearing Spacer) - 1) Position drive pinion in carrier and install bearing spacer. Place front pinion bearing in position on pinion gear, hold gear fully forward, and drive bearing over pinion until seated. Apply grease to lip of pinion by tapping with a soft hammer. Install pinion washer and nut. Before tightening nut (when pinion preload is zero), check oil seal drag using a torque wrench. Tighten pinion nut as follows:
Application                                       Ft. Lbs. (mkg)
808 (W/1300 cc)...................................   87 (12)

INSTALLING DIFFERENTIAL ASSEMBLY

RX-4....................................................  101(14)
B1600, RE (Rotary Pick-Up)...................  145(20)
All Others..............................................   94(13)
2) With nut tightened, check preload using a torque wrench mounted on pinion nut. If preload is not as specified (see Axle Assembly Specifications), continue tightening nut and checking preload until specified preload is obtained. CAUTION - Preload builds quickly. Nut should be tightened a little at a time and preload checked after each slight amount of tightening.
Case Assembly - 1) On all models except RX-4, install a thrust washer on each differential side gear and install into case. Through openings in gear case, insert pinion gears exactly 180 degrees opposite each other. Rotate pinion gears 90 degrees so holes in gears line up with pinion shaft holes in gear case. Insert pinion shaft through case and pinion gears.

ADJUSTING BEARING PRELOAD (CASE SPREAD)

2) On RX-4 models, install a thrust washer on each differential side gear and install into case halves. Position pinion gears on spider and install spider into differential case half. Align identification marks, mate case halves, and install and tighten retaining bolts.
3) On all models, check backlash between side gears and pinion gears. Backlash should be less than .004" (.1 mm); if not, install selective thrust washers to bring backlash within specifications. Washers are available in thicknesses of .063" (1.6 mm), .067" (1.7 mm), .071" (1.8 mm), .079" (2.0 mm), .083" (2.1 mm), and .087" (2.2 mm). NOTE - Always use some thickness thrust washer for both side gears.
4) If equipped with thrust block, remove pinion shaft, install thrust block, and reinstall pinion shaft. On all models except RX-4, drive lock pin into case to secure pinion shaft. Using a punch, shake lock pin into case to secure pinion shaft. Using a punch, stake lock pin hole to prevent pin from working loose. On all models, mount ring gear on case, then install and tighten ring gear attaching bolts. If removed, instal differential side bearings.
Backlash & Side Bearing Preload - 1) Place differential case assembly into carrier making sure timing marks on ring and pinion gears are aligned. Install bearing adjusters and bearing caps, then tighten bearing cap nuts or bolts finger tight. Turn adjusters with a suitable spanner wrench (49 0259 720) until bearing end play is eliminated and some backlash exists between ring gear and pinion. Slightly tighten one bearing cap nut or bolt on each side carrier.
2) Mount a dial indicator to carrier flange so button of indicator contacts of the ring gear teeth at a right angle then check backlash between ring and pinion gears. Using the spanner wrench, turn both bearing adjusters equally until backlash is as specified in Axle Assembly Specifications.
3) Differential bearing preload (case spread) is obtained by tightening both bearing adjusters equally.  Tighten adjusters until the distance between pilot section of side bearing caps in as specified in Axle Assembly Specifications. Tighten bearing cap nuts or bolts, then recheck backlash adjustement. Make a gear tooth pattern check to insure correct assembly, then install adjuster lock plates on bearing caps.