Drive Axle Buick Roadmaster VIII

AXLE RATIO & IDENTIFICATION

Rear axle identification information is stamped on forward side of left or right axle tube on all models except Fleetwood. (Scheme 1) On Fleetwood, an identification code is stamped on rear of right axletube 3" (76 mm) from differential housing or backside of right caliper support plate.

AXLE RATIO IDENTIFICATION

Scheme 1

DESCRIPTION & OPERATION

Drive axle is a semi-floating, hypoid-gear type with integral housing. Center line of pinion is set below center line of ring gear. A removable steel cover, bolted to rear of housing, permits servicing differential case without removing axle assembly from vehicle. On ABS and Trac-tion Control System (TCS) equipped vehicles, a sensor is threaded into axle housing just behind drive pinion yoke. Sensor receives input signal from a sensor ring pressed onto the drive pinion gear stem.

Note. For positive traction differential overhaul procedures, see DRIVE AXLE - POSITIVE TRACTION article in the DRIVE AXLE Section.

LUBRICATION

Fill differential with 80W-90 GL-5 Gear Lubricant (1052271 ). See LUBRICATION CAPACITIES table. On Caprice and Roadmaster, add 4 ounces (.12L) of limited slip additive (1052358).

LUBRICATION CAPACITIES (1)

Removal

1. Raise and support vehicle. Remove rear wheels and brake drums (or disc calipers and rotors). Remove housing cover and drain lubricant from differential.
2. Remove pinion shaft lock bolt and pinion shaft. Push axle shaft toward center of vehicle and remove "C" lock from inner end of shaft. Carefully remove axle shaft from housing.
3. Insert Bearing and Seal Remover (J-23689 on Roadmaster and Fleetwood 8 1/2" axle, J-29712 on Fleetwood 9 1/2" axle; or J-22813-01 on all other axles) into bore. Position remover behind bearing so tangs engage bearing outer race. Using a slide hammer, remove bearing and seal. Discard bearing and seal.

Installation

1. Lubricate NEW bearing with gear oil. Using Bearing Installer (J-23690 on Roadmaster and Fleetwood 8 1/2" axle; J-29709 on Fleetwood 9 1/2" axle; or J-23765 on all other axles) and Handle (J-8092 ), install bearing. Bearing is properly seated when installer bottoms against bore.
2. Lubricate NEW seal with gear oil. Position seal on Seal Installer (J-29713 on Fleetwood 9 1/2" axle; J-23771 on 7 1/2" and 7 5/8" axles; or J-21128 on all other axles). Drive seal until flush with axle tube.
3. To complete installation, reverse removal procedure. Pull axle shaft outward after installing "C" lock to seat lock in counterbore of axle side gear. Install pinion shaft and lock screw.

Scheme 2

1. Raise and support vehicle. Scribe an alignment mark on drive shaft, companion flange, pinion and pinion nut for installation reference. Remove drive shaft.
2. Using an INCH-lb. torque wrench, measure and record pinion bearing preload. Remove pinion nut and washer. Using a puller, remove companion flange. (Scheme 2) Pry seal out of housing.

1. Pack seal lip of NEW seal with lithium-based, extreme-pressure grease. Drive seal into housing until seated against shoulder. Install companion flange, washer and pinion nut. NOTE: If preload specification is exceeded, a new collapsible spacer must be installed and nut retightened until correct preload is obtained.
2. Gradually tighten pinion nut until all end play is removed. Turn drive pinion several times to seat bearings. Ensure pinion bearing preload is 3-5 INCH lbs. (.3-.6 N.m) more than reading obtained during removal. Install drive shaft.

Scheme 3

1. Raise and support vehicle. Remove rear tires. Place supports under rear axle assembly. Disconnect shock absorbers from axle. On Fleetwood, Caprice and Roadmaster, disconnect level control switch link and speed sensor (if equipped).
2. On all models, loosen parking brake cable adjuster nut. Remove parking brake cables from adjuster and body clips. Remove stabilizer bar. Scribe alignment mark on companion flange and drive shaft for installation reference.
3. Remove drive shaft. Remove brakeline junction block bolt from axle. Disconnect brakelines from junction block and wheel cylinders/calipers. WARNING: Use care when removing suspension springs. Uncontrolled expansion of coil springs could cause bodily injury or damage to vehicle.
4. Disconnect brakeline from axle mounting clips. Remove or clear brakelines away from axle assembly. On Fleetwood, Caprice and Roadmaster, disconnect upper control arms from axle assembly. On Camaro and Firebird, disconnect lower control arms, rear axle tie rod and torque arm from axle.
5. On all models, lower axle and remove springs. Remove brake drums and backing plates (or calipers and rotors) and support out of way. Carefully lower axle and remove from vehicle.

To install, reverse removal procedure. Use a NEW cover gasket when installing cover. Refill axle housing with proper lubricant. Bleed and adjust brakes.

OVERHAUL

Note. For positive traction differential overhaul procedures, see DRIVE AXLE - POSITIVE TRACTION article in the DRIVE AXLES Section. The Auburn limited-slip differential case is not serviceable and MUST be replaced as an assembly.

Differential Case Assembly

1. Remove axle shafts. See «AXLE SHAFT & BEARING»(/buick/roadmaster/viii-1991-1996/remont/differentials-drive-axles/#drive-axle) under REMOVAL & INSTALLATION. Check ring and pinion gear backlash and pinion bearing preload. This will indicate gear or bearing wear, or an error in backlash or preload setting. Remove speed sensor (if equipped).
2. Mark differential bearing caps and housing for reassembly reference. Remove caps and differential case from housing. Remove bearing cups and shims. Keep each shim set with proper bearing cap for reassembly. On Fleetwood 9 1/2" ring gear, remove side bearing adjusting nut.
3. Remove differential pinion shaft, gears, and side gears with thrust washers. (Scheme 3) Keep components in order for reassembly. Remove ring gear bolts (left-hand threads). Tap ring gear off differential case using soft drift and hammer.
4. If necessary, remove speed sensor ring (if equipped). Remove nut and companion flange. «COMPANION FLANGE & OIL SEAL»(/buick/roadmaster/viii-1991-1996/remont/differentials-drive-axles/#drive-axle) under REMOVAL & INSTALLATION. Remove drive pinion and front bearing. If necessary, remove pinion bearing cups from housing using a brass drift. Press drive pinion out of rear bearing and note thickness of pinion depth shim pack.

Scheme 4

Scheme 5

1. Thickness of drive pinion rear bearing shim must be determined whenever a new axle housing, ring and pinion set, or pinion bearings and races are installed. Depth of mesh is determined using Pinion Setting Gauge Set (J-21777 ). See «PINION DEPTH GAUGE SET»(/buick/roadmaster/viii-1991-1996/remont/differentials-drive-axles/#drive-axle) table. NOTE: Checking procedure for different axle sizes is the same. However, gauge set components vary between axles.
2. If removed, lubricate and install pinion bearings into races. Install lubricated pinion bearings. Position gauge plate and rear pinion bearing pilot on preload stud. Install assembly through rear pinion bearing, front pinion bearing and front pinion bearing pilot. (Scheme 4)
3. Install hex nut until snug. Rotate bearings to ensure proper seating. Hold preload stud stationary with a wrench on flats. Tighten hex nut until 20 INCH lbs. (2.3 N.m) is required to rotate bearings. PINION DEPTH GAUGE SET Tool Name & Application Tool Number Arbor J-21777-1 Dial Indicator J-8001 Gauge Plate 7 1/2" & 7 5/8" Ring Gear J-21777-11 8 1/2" Ring Gear J-21777-29 9 1/2" Ring Gear J-21777-85 Front Pinion Bearing Pilot J-21777-42 Preload Stud J-21777-43 Rear Pinion Bearing Pilot 7 1/2" & 7 5/8" Ring Gear J-21777-40 8 1/2" Ring Gear J-21777-35 9 1/2" Ring Gear J-21777-8 Side (Differential) Bearing Gauge Discs 7 1/2", 7 5/8" & 8 1/2" Ring Gears J-21777-45 9 1/2" Ring Gear J-21777-86
4. Mount side bearing gauging discs on ends of arbor. Place arbor into carrier ensuring discs are properly seated. Install side bearing caps and bolts. Tighten bolts to avoid movement.
5. Position dial indicator on mounting post of arbor with contact button resting on top surface of plunger. Preload dial indicator one-half revolution and tighten. Place plunger onto gauging area of gauge plate.
6. Rock plunger rod slowly back and forth across gauging area until dial indicator reads greatest deflection. Set indicator to zero. Repeat rocking action several times to verify setting. Once zero reading is obtained, remove plunger from gauging area.
7. Dial indicator will now read required pinion shim thickness for a "nominal pinion". Record this reading. Check drive pinion for painted or stamped markings on pinion stem or a stamped code number on small end of pinion gear. (Scheme 5)
8. If marking is a positive number, subtract that many thousandths from indicator reading. If marking is a negative number, add that many thousandths to indicator reading. This will be the thickness of rear pinion bearing shim pack.
9. If no markings are found on pinion, use dial indicator reading as shim thickness. Remove bearing caps and gauging tools from housing. Place selected shim pack on drive pinion. Using a press, install lubricated pinion bearing on pinion shaft.

Differential Case Reassembly

1. Install speed sensor ring (if equipped). Install ring gear on case with NEW bolts. Alternately tighten bolts to pull ring gear into position on case. Place side gear thrust washers over side gear hubs.
2. Install assemblies into case in their original positions. Install pinions and thrust washers into case. Install pinion shaft and lock bolt. Using bearing installer, install side bearings onto differential case.

Differential Shim Selection

1. Measure thickness of original side bearing preload shims. Select a standard .17" (4.3 mm) service spacer and service shims with a total thickness slightly less than original shims. Standard service shims are steel and are available from .040-.082" (1.02-2.08 mm). Production shims are cast iron and available from .210-.272" (5.33-6.91 mm). NOTE: DO NOT attempt to reuse production shims, because they may break when tapped into position.
2. Install differential case in housing. Install spacer between each bearing cup and housing with chamfered edge of spacer against housing. Install left bearing cap loosely so that differential case is free to move. With left bearing race and spacer against housing, install both left and right service shims between right bearing race and service spacer.
3. Insert progressively larger feeler gauges between right service spacer and shim pack until a slight drag is felt. Total thickness of required shim pack is equal to feeler gauge thickness plus shim thickness used in step 1). Remove differential case, shims and spacers from axle housing.

Pinion Preload Adjustment

1. Install a NEW collapsible spacer over pinion stem. Position pinion in housing. While holding pinion forward, carefully drive front pinion bearing onto pinion shaft until a few threads are exposed.
2. Install NEW oil seal, companion flange, washer and nut. Tighten nut until end play is removed. Rotate pinion several times to seat bearings.
3. Check preload using an INCH-lb. torque wrench. Continue tightening nut and checking preload until correct preload is obtained. DO NOT overtighten. See «AXLE ASSEMBLY SPECIFICATIONS»(/buick/roadmaster/viii-1991-1996/remont/differentials-drive-axles/#drive-axle) table. CAUTION: If preload is exceeded, a NEW collapsible spacer must be installed and nut retightened until proper preload is obtained.

Scheme 6

1. With pinion depth set and pinion installed, place differential case and ring gear assembly into axle housing. Select 2 shims with a combined thickness equal to that of service shims and feeler gauge used in differential shim selection procedure. Install shims and spacers between bearing cups and housing. Install differential bearing caps and tighten cap bolts.
2. Rotate differential case several times to seat bearings. Check backlash using a dial indicator. Increase or decrease shim size where necessary to correct backlash reading. (Scheme 6) Recheck backlashat 4 points equally spaced around ring gear. Ensure that variation between points does not exceed.002" (.05 mm).

Differential Bearing Preload

1. On Fleetwood models with 9 1/2" ring gear, tighten the differential bearing adjusting nut using Wrench (J-24429 ), until the nut just contacts the shim. Tighten the nut 3 additional slots. Install bearing caps and tighten to correct specification. Refer to the «TORQUE SPECIFICATIONS (DIFFERENTIAL)»(/buick/roadmaster/viii-1991-1996/remont/differentials-drive-axles/#drive-axle) . After adjusting backlash, install and tighten bearing adjusting nutlock bolt.
2. On all other ring gears, remove differential bearing caps and increase left and right shim sizes .004" (.10 mm). Gentle tapping may be necessary to install second shim. Ensure shims are seated and differential turns freely.
3. On all ring gears, using gear marking compound, check gear tooth contact pattern to verify proper assembly and adjustment. Complete necessary settings, and install axle shafts. Install differential cover and fill with lubricant. CAUTION: Avoid damaging seals when installing axle shafts.

AXLE ASSEMBLY SPECIFICATIONS

AXLE ASSEMBLY SPECIFICATIONS

TORQUE SPECIFICATIONS (DIFFERENTIAL)

TORQUE SPECIFICATIONS (DIFFERENTIAL)

TORQUE SPECIFICATIONS (REAR AXLE - CAMARO & FIREBIRD)

TORQUE SPECIFICATIONS (REAR AXLE - CAMARO & FIREBIRD)

TORQUE SPECIFICATIONS (REAR AXLE - CAPRICE & ROADMASTER)

TORQUE SPECIFICATIONS (REAR AXLE - CAPRICE & ROADMASTER)

TORQUE SPECIFICATIONS (REAR AXLE - FLEETWOOD)

TORQUE SPECIFICATIONS (REAR AXLE - FLEETWOOD)

See also:
• DRIVE AXLE - POSITIVE TRACTION
• LUBRICATION CAPACITIES