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CONTENTS

REAR AXLE ALIGNMENT CHECKING PROCEDURE
REAR AXLE ASSEMBLY (7-1/4" and 8-1/4" RING GEAR)
REAR AXLE NOISE DIAGNOSIS
SERVICE DIAGNOSIS
SPECIFICATIONS 
SURE-GRIP DIFFERENTIAL
TIGHTENING REFERENCE

SERVICE DIAGNOSIS  (back to CONTENTS)

CONDITION

Possible Cause

Correction

Rear Wheel Noise

Wheel loose	Tighten loose nuts
Faulty, brinelled wheel bearing	Faulty or brinelled bearings must be replaced

Rear Axle Drive Shaft Noise

Misaligned axle housing	Inspect rear axle housing, alignment, correct as necessary
Bent or sprung axle shaft	Replace bent or sprung axle shaft
End play in drive pinion bearings	Refer to Pinion Bearing Pre-Load
Excessive gear lash between ring gear and pinion	Check adjustment of ring gear and pinion.  Correct as necessary
Improper adjustment of drive pinion shaft bearings	Adjust pinion bearings
Loose drive pinion companion flange nut	Tighten drive pinion flange nut to torque specified number under Tightening References.
Improper wheel bearing adjustment	Readjust as necessary
Scuffed gear tooth contact surfaces	If necessary, replace scuffed gears

Rear Axle Drive Shaft Breakage

Misaligned axle housing	Replace broken shaft after correcting rear axle housing alignment
Vehicle overloaded	Replace broken shaft.  Avoid excessive weight on vehicle
Abnormal clutch operation	Replace broken shaft, after checking for other possible causes.  Avoid erratic use of clutch
Grabbing clutch	Replace broken shaft.  Inspect clutch and make necessary repairs or adjustments

Differential Case Breakage

Improper adjustment of differential bearings	Replace broken case. Examine gears and bearings for possible damage.  At reassembly, adjust differential bearings
Excessive ring gear clearance	Replace broken case. Examine gears and bearings for possible damage.  At reassembly, adjust ring gear and pinion backlash
Vehicle overloaded	Replace broken case. Examine gears and bearings for possible damage.  Avoid excessive weight on vehicle
Erratic clutch operation	Replace broken case. After checking for other possible causes, examine gears and bearings for possible damage.  Avoid erratic use of clutch

Scoring of Differential Gears

Insufficient lubrication	Replace scored gears.  Scoring marks on the pressure face of gear teeth or in the bore are caused by instantaneous fusing of the mating surfaces.  Scored gears should be replaced.  Fill rear axle to required capacity with required lubricant.  See Specifications section
Improper grade of lubricant	Replace scored gears.  Inspect all gears and bearings for possible damage.  Clean out and fill rear axle to required capacity with required lubricant.  See Specifications section
Excessive spinning of one wheel	Replace scored gears.  inspect all gears, pinion bores and shaft for scoring, or bearings for possible damage.  Service as necessary.

Loss of Lubricant

Lubricant level too high	Drain excess lubricant by removing filler plug and allow lubricant to level at lower edge of filler plug hole
Worn axle shaft oil seals	Replace worn oil seals with new ones.  Prepare new seals before replacement
Cracked rear axle housing	Repair or replace housing as required
Worn drive pinion oil seal	Replace worn drive pinion oil seal with a new one
Scored and worn companion flange	Replace worn or scored companion flange and oil seal
Axle cover not properly sealed	Remove cover and clean flange and reseal

Overheating of Unit

Lubricant level too low	Refill rear axle
Incorrect grade of lubricant	Drain, flush and refill rear axle with correct amount of the proper lubricant.  See Lubrication section
Bearings adjusted too tightly	Readjust bearings
Excessive wear in gears	Check gears for excessive wear or scoring.  Replace as necessary
Insufficient ring gear to pinion clearance	Readjust ring gear and pinion backlash and check gears for possible scoring

Tooth Breakage (Ring Gear and Pinion)

Overloading	Replace gears.  Examine other gears and bearings for possible damage.  Replace parts as needed.  Avoid overloading of vehicle
Erratic Clutch Operation	Replace gears, and examine remaining parts for possible damage.  Avoid erratic clutch operation
Ice-spotted pavements	Replace gears.  Examine other gears and bearings for possible damage.  Replace parts as required
Improper adjustment	Replace gears.  Examine other gears and bearings for possible damage.  Make sure ring gear and pinion backlash is correct

Rear Axle Noise

Insufficient	Refill rear axle with correct amount of the proper lubricant.  See Lubrication section.  Also check for leaks and correct as necessary
Improper ring gear and pinion adjustment	Check ring gear and pinion tooth contact
Unmatched ring gear and pinion	Remove unmatched ring gear and pinion  Replace with a new matched ring gear and pinion set
Worn teeth on ring gear and pinion	Check teeth on ring gear and pinion for contact.  If necessary, replace with new match set
Loose drive pinion bearings	Adjust drive pinion bearings
Loose differential gear bearings	Adjust differential gear bearings
Misaligned or sprung ring gear	Check ring gear for runout
Loose carrier cap screws	Tighten to specifications

REAR AXLE NOISE DIAGNOSIS  (back to CONTENTS)

Most rear axle failures are relatively simple to locate and correct, although rear axle noise is a little more difficult to diagnose and make the necessary repairs. The most essential part of rear axle service is proper diagnosis of the problem.

All rear axles are noisy to a certain degree. Axles can be noisy if they are not properly adjusted or lack lubrication. Usually, when new improperly set gears are noisy, the disturbing noise can be “adjusted out”.

If the axle noise complaint is made within the first 1,500 miles (2413 km), and the gears are not scored due to lack of lubrication, the gear adjustment should be checked and corrected if necessary. Poor tooth pattern, incorrect drive gear backlash and loose pinion nuts are the primary causes of gear noise in new cars. Regardless of what you’ve heard to the contrary, noisy gears will not get quieter with added mileage ... they will stay the same or get worse.

Slight axle noise heard only at certain speeds or under remote conditions must be considered normal. Axle noise tends to “peak” at varying speeds and the noise is not always indicative of trouble in the axle.

If noise is present in an objectionable form, loud or at all speeds, an effort should be made to isolate the noise as being in one particular unit of the vehicle. Many noises, reported as coming from the rear axle actually originate from other sources such as tires, road surfaces, wheel bearings, engine, transmission, exhaust, propeller shaft vibration, universal joint noise or body drumming. A thorough and careful check should be made to determine the source of the noise before any disassembly and teardown of the rear axle is attempted.

Axle noises normally fall into two categories; gear noise and bearing noise. The complete isolation of noise in any one unit requires considerable skill and previous experience. Eliminating certain type noises often baffle even the most experienced personnel. Often such practices as raising tire pressures to eliminate tire noise, listening for the noise at varying speeds under different load conditions such as; drive, float and coast, and under certain highway conditions, will aid in detecting axle shaft bearing noise.

To make a good diagnostic check for rear axle noise a thorough road test is necessary. Select a level smooth blacktop road. This will reduce tire noise and body drumming. Drive the car far enough to thoroughly warm up the axle to normal operating temperature.

Drive the car and note speed at which noise occurs. Then stop car and, with clutch disengaged or automatic transmission in neutral, run engine slowly up and down through engine speeds, corresponding to car speed at which noise was most pronounced, to determine if it is caused by exhaust roar, or other engine conditions. Repeat, while engaging and disengaging clutch (transmission in neutral), to determine if noise can only be isolated by removing propeller shaft and operating transmission in high.

Tire Noise
Tire noise is often mistaken for rear axle noise even though the noisy tires may be located on the front wheels. Tires that are unbalanced or worn unevenly or have surfaces of non-skid type design, or worn in a saw tooth fashion are usually noisy and often produce noises that seem to originate in the rear axle.

Tire noise changes with different road surfaces, but rear axle noise does not. Inflate all tires to approximately 50 pounds pressure (345 kPa) for test purposes only.) This will materially alter noise caused by tires, but will not affect noise caused by rear axle. Rear axle noise usually ceases when coasting at speeds under 30 miles per hour (48 km/h); however, tire noise continues, but with lower tone, as car speed is reduced. Rear axle noise usually changes when comparing drive and coast, but tire noise remains about the same.

Distinguish between tire noise and differential noise by noting if noise varies with various speeds or sudden acceleration and deceleration; exhaust and axle noise show variations under these conditions while tire noise remains constant and is more pronounced at speeds of 20 to 30 miles per hour (32 to 48 km/h). Further check for tire noise by driving car over smooth pavements or dirt roads (not gravel) with tire at normal pressure. If noise is caused by tires, it will noticeably change or disappear and reappear with changes in road surface.

Front Wheel Bearing Noise
Loose or rough front wheel bearings will cause noise which may be confused with rear axle noises; however, front wheel bearing noise does not change when comparing drive and coast. Light application of brake while holding car speed steady will often cause wheel bearing noise to diminish, as this takes some weight off the bearing. Front wheel bearings may be easily checked for noise by jacking up the wheels and spinning them, also by shaking wheels to determine if bearings are loose.

Rear suspension rubber bushings and spring insulators help to dampen out rear axle noise when properly and correctly installed. Check to see that no metallic interference exists between the springs and spring hangers, shackles or “U” bolts. Metal to metal contact at those points may result in telegraphing road noise and normal axle noise which would not be objectionable if properly installed and tightened to specifications.

Gear Noise
The differential side gears and pinions are not a source of noise during normal driving, since the mesh condition changes too slowly to be heard. They will however, emit an audible howl during high rate differential action, as when one rear wheel spins while the other is stationary. This audible howl is not abnormal, but should be regarded as a warning since prolonged high rate differential action can result in extensive damage from seizure of differential components.

Abnormal gear noise can be recognized easily because it produces a cycling tone and will be very pronounced through the speed range in which is occurs. Gear noise may be developed under one or more of the following conditions, “drive”, “road load”, “float” or “coast”. Gear noise usually tends to peak in a narrow speed range or ranges. Gear noise is more prominent between 30 to 40 mph (48 to 64 km/h) and 50 to 60 mph (80 to 96 km/h). Abnormal gear noise is quite rare and if present it usually originates from scoring of the ring and drive pinion gear as a result of insufficient or improper lubrication of the axle assembly. If the gear noise is on coast at all speeds, check for a loose pinion nut and readjust per this manual if necessary.

When objectionable axle noise is heard, note the driving condition and speed range. Remove the housing cover. Perform a tooth contact pattern check to determine if the best possible pattern has been obtained. If pattern is found to be unacceptable, reshim and adjust to obtain the best possible tooth pattern. If after readjustment noise still persists, replace with new gear set.

Pre-Disassembly Investigation
A close examination of the rear axle assembly prior to disassembly can often reveal valuable information as to the extent and type of repairs or adjustment necessary. This information coupled with the road test results will provide a basis for determining the degree of disassembly required. Since the most frequent causes of axle noise are improper backlash or differential bearing preload, or both, a few simple adjustments may be all that is necessary to correct the complaint.

Therefore, before disassembly the following check should be made; drive gear and pinion backlash, pinion bearing preload, and tooth contact pattern and these results recorded and analyzed. It is felt that these measurements and their results will aid you in making the necessary repairs to the axle assembly.

Bearing Noise (Drive Pinion and Differential)
Defective or damaged bearings generally produce a rough growl or grating sound, that is constant in pitch and varies with the speed of the vehicle. This fact will allow you to diagnose between bearing noise and gear noise.

Drive pinion bearing noise resulting from defective or damaged bearings can usually be identified by a constant rough sound. Front pinion bearing noise is usually most pronounced on “coast”, whereby rear pinion bearing is loudest on “drive”. Pinion bearings are rotating at a higher rate of speed than the differential side bearings or the axle shaft bearings. These particular noises can be picked up best by road testing the vehicle in question on a smooth road (black top). However, extreme caution should be taken not to confuse tire noise with bearing or gear noise. If doubt should exist tire treads should be examined for irregularities that will often produce such noise.

Differential bearing noise will usually produce a constant rough tone which is much slower than the noise caused by the pinion bearings.

Rear Wheel Bearing Noise
Defective or damaged rear wheel bearings produce a vibration or growl which continues with car coasting and transmission in neutral. A brinneled rear wheel bearing causes a whirring noise. Spalled rear wheel bearings normally produce a noise similar to a growl, created from either flaked or pitted rollers or bearings races. Unless the damage is severe, rear axle bearing noise is seldom heard above 30 mph (48 km/h).

If the noise in question cannot be isolated an inspection of bearings will be necessary.

Knock at Low Speeds
Low speed knock is usually caused by brinneled universal joints or differential side gear hub to counterbore clearance being too great. The knock caused by excessive side gear hub to counterbore clearance will be on coast only. Inspect and replace universal joint or differential case and side gear as required.

Backlash Clunk
An audible metallic clunk accompanied by a bump can occur when the foot is abruptly lifted from the accelerator pedal, or when the pedal is abruptly depressed from its free position, while driving in the 30-55 mph. (48-89 km/h) range.

An objectionable level of clunk and bump can be helped by reducing the amount of axial looseness at the differential side gears, using select thickness thrust washers. The procedure is covered in the Differential Reconditioning Section.

Engine and Transmission Noise
Sometimes noises which seem to originate in the rear axle are actually that of the engine or transmission. To diagnose which unit is actually causing the noise, observe the approximate vehicle speed and conditions under which the noise is most pronounced; stop the vehicle in a quiet place to avoid any interfering noises. With engine running and transmission in neutral, run engine slowly up and down through engine speeds corresponding to approximate car speed at which the noise was most pronounced. If a similar noise is produced in this manner it usually can be assumed that the noise was caused by the engine or transmission and not by the rear axle.

Propeller Shaft Vibration
Objectional vibrations at high speed may be caused by a propeller shaft that is out of balance or worn universal joints. Out of balance may be due to a damaged or bent shaft. Refer to Group 16 -  Propeller Shaft and Universal Joint in this manual.

REAR AXLE ALIGNMENT CHECKING PROCEDURE

The following describes the procedure for checking rear axle alignment to determine if a complaint of abnormal rear tire wear is the result of a “bent” rear axle housing:
(1) Raise both rear wheels off ground using a frame contact hoist.
(2) Place a one inch long piece of masking tape in the center of each tire tread for use as “reference marks”.
(3) With both “reference marks” pointing to front of vehicle, measure the distance between the outside edges of the two pieces of tape. Record this measurement as the “front of tire” (FTR) reading.
(4) Rotate the rear wheels so that the “reference marks” of each rear wheel now point to the rear of vehicle. Measure the distance between the outside edges of the two pieces of tape and record this measurement as the “rear of tire” (RTR) reading.
(5) Subtract the “rear of tire” measurement from the “front of tire” measurement to obtain the “toe out” condition of the axle being checked. The specification is 1/16 inch toe-in to 3/16 inch toe-out.
(6) Rotate both rear wheels so that the “reference marks” are pointing down. Measure the distance between the outside of the two pieces of tape and record this measurement as “bottom of tire” (BTR) reading.
(7) Average the sum of the “front of tire” reading (FTR) and the “rear of tire” reading (RTR), then from this average figure subtract “bottom of tire” reading (BTR) to obtain the camber. The specification is -1/16 to +3/32 inch camber.

FTR + RTR
       2

-BTR = ± Camber

If BTR is smaller than the average figure, the camber reading is positive +. If the BTR is larger than the average figure, the camber reading is negative ( - ).

Tire Wheel Balance
Refer to, “Wheels-Tires”, Group 22 in this manual.

REAR AXLE ASSEMBLY 7-1/4 IN. AND 8-1/4 IN. RING GEAR  (back to CONTENTS)

SPECIFICATIONS  (back to CONTENTS)

ITEM	7-1/4" AXLE	8-1/4" AXLE
TYPE	Semi-Floating Hypoid	Semi-Floating Hypoid
Ring Gear Diameter	7.250"	8.250"
Number of Teeth
Drive Gear	43	47
Pinion	19	21
Ratio to 1	2.26	2.24
Number of Teeth
Drive Gear		47
Pinion		16
Ratio to 1		2.94
PINION BEARINGS
Type	Taper Roller	Taper Roller
Number used	Two	Two
Adjustment	Collapsible Spacer	Collapsible Spacer
Pinion Bearing Preload New Bearings	15-30 in. lbs. (2 to 3 N•m)	20-35 in. lbs. (2 to 4 N•m)
Used Rear and New Front	10-25 in. lbs. (1 to 3 N•m)	10-25 in. lbs. (1 to 3 N•m)
DIFFERENTIAL	Conventional	Conventional or Sure-Grip
Bearings (Type)	Taper Roller	Taper Roller
Number Used	Two	Two
Preload Adjustment	Threaded Adjuster	Threaded Adjuster
RING GEAR AND PINION	Hypoid	Hypoid
Serviced In	Matched Sets	Matched Sets
Pinion Depth of Mesh Adjustment	Select Shims	Select Shims
Pinion and Ring Gear Backlash	.003-.006" At Point of Minimum Backlash	.005-.008" At Point of Minimum Backlash
Runout-Differential Case	.003"	.003"
Ring Gear Backface	.005"	.005"
WHEEL BEARINGS
Type	Straight Roller	Straight Roller
Adjustment	None	None
End Play	Built-In	Built-In
Lubrication	Rear Axle Lubricant	Rear Axle Lubricant
LUBRICATION
Capacity	2.5 Pints (1.18 liter)	4.4 Pints (2.08 liter)
Type	Multi-Purpose Gear Lubricant, as defined by the American Petroleum Institute GL-5 should be used on all rear axles; such a lubricant is available under Part No. 4318058 MOPAR Hypoid Gear Lubricant or equivalent.  In Sure-Grip Differentials 4 ounces (.1183 liters) of MOPAR Hypoid Gear Oil Additive Friction Modifier, Part No. 4318060 or equivalent must be included with every refill.

TIGHTENING REFERENCES  (back to CONTENTS)

7-1/4" Axle	Foot Pounds	Inch Pounds	N•m
Differential Bearing Cap Bolts	45		61
Ring Gear to Differential Case Bolts (Left Hand Thread)	70		95
Drive Pinion Flange Nut	210 (Min.)		285
Carrier Cover Bolts	35		47
Brake Support Plate Retaining Nuts	35		47
Propeller Shaft Bolts (Rear)		170-200	19-23
Spring Clip (U Bolt) Nuts	45		61
Wheel Stud Nuts	85 (Max.)		115
Shock Absorber Stud Nuts (Lower)	50		68

8-1/4" Axle	Foot Pounds	Inch Pounds	N•m
Differential Bearing Cap Bolts	100		136
Ring Gear to Differential Case Bolts	70		95
Drive Pinion Flange Nut	210 (Min.)		285
Carrier Cover Bolts		250	28
Brake Support Plate Retaining Nuts	35		47
Propeller Shaft Bolts (Rear)		170-200	19-23
Spring Clip (U Bolt) Nuts	45		61
Wheel Stud Nuts	85		115
Shock Absorber Stud Nuts (Lower)	50		68

SPECIAL TOOLS  (back to CONTENTS)