Monday, February 13, 2012

Austin Marina 1973-73 Drive Axles Repair Guide

1973-74 Austin Marina

Rear axles are hypoid design with center line of pinion set below centerline of ring gear. The axle shafts, pinion and differenctial assemblies can be serviced without removing axle from vehicle. All differential adjustments are performed using shims. No adjustments for axle shaft end play is necessary.
Only one basic axle design is used on these models. To determine axle ratio, divide number of ring gear teeth by number of pinion gear teeth.
1) With rear of vehicle raised and wheel removed, remove axle shaft nut and washer. Remove screws retaining brake drum and remove drum. Withdraw rear hub from axle shaft using suitable tool. Disconnect handbrake cable and brake pipe. Remove nuts, washers and bolts retaining brake backplate to axle housing.
2) Note installed position of drip lip in relation to brake slave cylinder and remove oil catcher and backplate assembly. Remove rear hub oil seal and housing assembly. Remove oil seal from housing using suitable tool. Remove axle shaft key and place container under axle to collect oil spillage. Withdraw axle shaft from housing, using suitable puller. Remove inner oil seal and press bearing from axle shaft.
3) Pack bearing with lithium based grease and dip new oil seal in light oil before reassembling. Install new oil seal with lip of seal facing inwards. Press bearing onto axle shaft until dimension from bearing to threaded end of axle shaft is to specifications. Continue assembling in reverse of disassembly using a new rear hub joint washer and using "Lactite LT 270" or equivalent on axle shaft nut.

1)  Raise and support rear of vehicle. Mark propeller shaft and pinion flanges for correct realignment. Disconnect propeller shaft and remove flange nut split pin. Retain flange using suitable tool and remove nut and washer.
2) Place container under flange to collect oil spillage and remove flange and oil seal. To install reverse removal procedure noting the following: Soak new seal in light oil for one hour before installing. Install seal with lip of seal facing inwards.

Remove both axle shafts and mark differential pinion and propeller shaft for proper realignment on assembly. Disconnect propeller shaft. Place container under axle assembly to collect oil and remove nuts and washers retaining carrier to axle housing. Remove carrier. To reinstall, reverse removal procedure, using a new gasket and suitable gasket sealer.

1) With carrier removed, mount unit upright in a vise and mark bearing caps for correct reassembly. Remove bearing cap bolts, washer and caps. Assemble suitable axle stretcher (18G-131) on unit casing and stretch unit case by tightening turnbuckle three or four flats until differential carrier can be levered out and bearing shims and caps removed. CAUTION - To avoid damaging case, do not spread any more than necessary. Maximum stretch is .008" (.20 mm). Do not pry against stretcher.
2) Remove gear carrier bearing caps and mark ring gear and carrier to ensure correct replacement. Remove ring gear retaining bolts and ring gear. Drive out pinion shaft locking pin, then drive out pinion shaft. Remove pinion gears and thrust washers. Remove differential gears and thrust washers. Remove drive flange nut cotter pin and drive flange nut. Using suitable puller, remove drive flange.
3) Press out drive pinion and remove pinion bearing shims and spacer. Using suitable press tools, remove inner bearing from pinion. Remove pinion head washer and drift out pinion outer bearing cup, bearing and oil seal. Drift out pinion inner bearing cup.
Clean and inspect all components for wear or damage. Ring and pinion gears, differential bearings and pinion bearings must be replaced as matched sets.

Side Bearing Preload - 1) Install differential bearing comes in gear carrier using suitable tool. Install two differential gear carrier using suitable tool. Install two differential gears in carrier, ensuring each thrust washer is correctly positioned. Position two pinion gears, one each side of carrier and mesh them with differential gears. Using on axle shaft inserted in a differential gear, turn gears and ensure two pinions rotate into mesh and align with pinion shaft hole in carrier. Install pinion shaft.
2) Press each pinion firmly into mesh with differential gears and, asses required pinion thrust washer thickness required to achieve ZERO backlash. Remove pinon shaft and pinions and install thrust washers. Reinstall pinion gears and shfts with thrust washers and check that zero backlash exists. Lubricate components and install pinion shaft locking pin and secure by peening metal of differential carrier.
3) Clean ring gear mounting and carrier face and install ring gear, tighten bolts. Assembly carrier bearing cups to bearings and position assembly in case; do not install bearing shims. Install bearing caps in correct position. Using dial indicator and suitable adapters, ensure that ring gear runout does not exceed specifications. Remove bearing caps and press differential bearing cups onto bearings and move carrier assembly to one side of case. Zero dial indicator and move carrier assembly fully in opposit direction. The indicator reading should be noted for future references as "Total Side Floor". Remove differential assembly from case.

Drive Pinion Depth - 1) Install inner and outer pinion bearing cups to case using suitable tools. Install pinion inner bearing to dummy pinion (18G-191 M). NOTE - Dummy pinion incorporate standard pinion head washer of .077" (1.95 mm) thickness. Oil bearing and install dummy pinion, outer bearing, tool spacer, washer and nut. Tighten nut gradually until bearing preload specification is obtained. Clean dummy pinion head and position dial indicator gauge foot of tool 18G-191 on dummy head and zero indicator.
2) Move dial indicator over center of one differential bearing bore and note reading. Repeat for opposite bearing bore.
Average these two measurements and perform the following calculation.
Average of bore measurements.................. .0002" (.051 mm)
PLUS dummy pinion washer allowance..... .077"  (1.956 mm)
Required size of pinion head washer ........  .079    (2.007 mm)
If the etched marking on pinon face is "N" (normal), no change to above dimension is required. If etched marking is positive (+), reduce size of required pinion washer by amount marked. If etched marking is negative (-), increase size required pinion washer by amount marked. Remove dummy pinion and remove inner bearing from dummy pinion.

Pinion Bearing Preload - 1) Place selected pinion head washer on pinion and install inner bearing using suitable tools. Oil bearing and install pinion in case. Install bearing spacer, chamfered end towards drive vlange. Install shims, oil and install outer bearing. Install drive flange washer and nut. Gradually tighten nut, but do not exceed torque specifications, and check preload during tightening operation.
2) Rotate flange to settle bearing and check preload with flange nut tightened to specifications. If preload is high, increase shim thickness. If preload is low, decrease shim thickness. NOTE - .001" shim thickness equals approximately 4 INCH lbs. (4.6 cmkg) preload. Remove drive flange nut and flange. Soak new oil seal in oil for one hour and then install seal. Install drive flange, washer and nut and tighten flange nut. Install new cotter pin.

Adjusting Backlash - 1) Place bearing cups on differential bearing and install carrier in case. Position dial indicator with suitable adapters on ring gear side of case. Move ring gear fully into mesh with pinion and zero indicator on rear of ring gear. Move ring gear and carrier in opposite direction until bearing ring gear side is butted in housing. The indicated measurement should be noted as the "In-out" mesh clearance.
2) Perform the following calculation:
"In-Out" mesh clearance 1..........................   .025" (.63 mm)
MINUS Specified backlash.........................  .005" (.13 mm)
Required ring gear side shim pack.............  .020" (.50 mm)
"Total Side Floot" 2....................................  .060"  (1.52 mm)
MINUS ring gear side shim pack...............  .020" (.50 mm)
Required shim pack opposite ring gear ...  .040" (1.02 mm)
1 - Value from 2) above
2 - Value from 2) under "Side Bearing Preload".
Add a value of .002" (.51 mm) to each shim pack calculated above for preload.

3) Stretch case specified amount and from calculations made above, select required shim pack. Install differential assembly in case with shim packs. Loosen case stretcher and remove. Install bearing caps as originally marked and tighten bolts. Rotate pinion to settle differential bearings and position dial indicator using suitable adapters to measure ring gear backlash. Measure backlash at several locations, it must be to specifications. If not, interchange shims from side to side to achieve specified backlash. NOTE - A movement of .002" (.05 mm) shim thickness from one bearing to the other will vary backlash by about .002" (.05 mm). Reinstall differential assembly in rear axle housing.