holmesfound some info for future references:
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
Chris SAny chance of you recording the knocking and placing it on youtube so we can all hear it? it would be a great help in diagnosis
holmeshi chris i dont have anyway of putting the noise on the net.Iam getting the mechanic to have another look today. the noise sounds very much like if your sitting in the car, and you get someone to knock the exhaust against the antiroll-bar it sounds like that, it gets quicker as the car gets quicker but not louder and is more noticeable as iam slowing down weather the clutch is depressed or not. i have had the car on the ramp with someone in it accelerating to 30mph or so while i hold each rear wheel in turn he said that i didnt stop with either wheel being held, hence my assumption that it may be the prop shaft.it doesnt matter if i go round corners or hard braking iam a bit con fused i will let you know wot happens after ive had a look at lunch. regards darren
Chris SIt does sound like the the propshaft hitting either the exhaust, rear ARB or a heatshield, perhaps the best way to try and describe the noises is that when hitting the exhaust its a bonk, the ARB is a clonk and the heatshield is a tonk,
btw, do you know anyone with a reasonably new digital camera? one that records sound onto its video? you could make a video soundtrack of the noise and post it on youtube as I did here
http://www.youtube.com/watch?v=t3kZav9C8_o
my camera is 5 years old though and lacks sound!
holmeshi chris it sounds like a clonk, the mechanics had a look and now they think it is the o/s/r driveshaft cv joint so iam gona take that off tonight and check. i took the one off my black syncro from the same side, and the grease in it had gone hard and you could roll it into little balls, iam kinda hoping i find the same again as this would at least give the prospect of being the problem. i dont know of anyone with a camera or recording device sorry, i do like those gauges though[
]. will let you know wot happens tonight regards darren
holmessorry chris do you also have a picture of the rear diff fluid filling point. ive looked but cannot be sure, iam gona check for metal fillings in the diff.cheers
Chris SHere you are, on the left is the VC, the right is the LH drive shaft flange, the fill plug is centre on photo, its a 17mm allen headed plug, I made a removal tool from a wheel bolt with 2 17mm nuts welded on
holmeshi chris i changed the rear diff oil lastnight there wasn’t anything large in the filler plug or the oil just a fine grey paste on the drain plug like you said. i was unable to test the cv joint as the heavens opened up as i was doing it. i wonder weather it may be one of the outer bearing in the diff, from looking at the picture you sent, or maybe the seal. i will try the outer cv joint when i get a moment. if all fails i will by a new radio and keep it turned up.[]
holmesremoved the rear wishbones, diff and main beam last night so iam well on the way for restoration of these parts next stop is renewing all the bushes bearings and seals on both the diff and the wishbones. dont suppose you know the part numbers of such items as i know you said you renovated yours.[]