LOW SPEED KNOCK
Low speed knock is generally caused by a worn U-joint or by worn side-gear thrust washers. A worn pinion shaft bore will also cause low speed knock.
DRIVELINE SNAP
A snap or clunk noise when the vehicle is shifted into gear (or the clutch engaged) can be caused by
- High engine idle speed.
- Transmission shift operation.
- Loose engine/transmission/transfer case mounts.
- Worn U-joints or C/V joints.
- Loose spring mounts.
- Loose pinion gear nut and yoke.
- Excessive ring gear backlash.
- Excessive side gear to case clearance.
The source of a snap or a clunk noise can be determined with the assistance of a helper. Raise the vehicle on a hoist with the wheels free to rotate. Instruct the helper to shift the transmission into gear. Listen for the noise, a mechanics stethoscope is helpful in isolating the source of a noise.
PINION GEAR DEPTH VARIANCE
| Original Pinion Gear Depth Variance | Replacement Pinion Gear Depth Variance | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 4 | 3 | 2 | 1 | 0 | +1 | +2 | +3 | +4 | |
| +4 | +0.008 | +0.007 | +0.006 | +0.005 | +0.004 | +0.003 | +0.002 | +0.001 | 0 |
| +3 | +0.007 | +0.006 | +0.005 | +0.004 | +0.003 | +0.002 | +0.001 | 0 | 0.001 |
| +2 | +0.006 | +0.005 | +0.004 | +0.003 | +0.002 | +0.001 | 0 | 0.001 | 0.002 |
| +1 | +0.005 | +0.004 | +0.003 | +0.002 | +0.001 | 0 | 0.001 | 0.002 | 0.003 |
| 0 | +0.004 | +0.003 | +0.002 | +0.001 | 0 | 0.001 | 0.002 | 0.003 | 0.004 |
| 1 | +0.003 | +0.002 | +0.001 | 0 | 0.001 | 0.002 | 0.003 | 0.004 | 0.005 |
| 2 | +0.002 | +0.001 | 0 | 0.001 | 0.002 | 0.003 | 0.004 | 0.005 | 0.006 |
| 3 | +0.001 | 0 | 0.001 | 0.002 | 0.003 | 0.004 | 0.005 | 0.006 | 0.007 |
| 4 | 0 | 0.001 | 0.002 | 0.003 | 0.004 | 0.005 | 0.006 | 0.007 | 0.008 |
PINION GEAR DEPTH VARIANCE
If installing a new gear, note the depth variance number of the original and replacement pinion. Add or subtract this number from the original depth shim/oil slinger to compensate for the difference in the depth variances. The numbers represent thousands of an inch deviation from the standard. If the number is negative, add that value to the required thickness of the depth shims. If the number is positive, subtract that value from the thickness of the depth shim.
Pinion Gear Depth Variance Chart: Note where Old and New Pinion Marking columns intersect. Intersecting figure represents plus or minus the amount needed.
DIFFERENTIAL BEARING PRELOAD AND GEAR BACKLASH
Differential side bearing preload and gear backlash is achieved by selective shims (2) (4) inserted between the bearing cup and the housing. The proper shim thickness can be determined using slip-fit Dummy Bearings 8398 in place of the differential side bearings and a Dial Indicator C-3339. Before measuring differential bearing preload and gear backlash, measure pinion gear depth and prepare pinion for installation. Pinion gear depth is essential to establishing gear backlash and tooth contact patterns. After measuring shim thickness to take up differential side play, install pinion and measure gear backlash shim thickness. Overall shim thickness is the dial indicator reading and preload specification added together. The gear backlash measurement determines the shim thickness used on the ring gear side of the differential case. Subtract gear backlash shim thickness from overall shim thickness to determine shim thickness for pinion gear side of the differential.
Scheme 84
Scheme 85
Scheme 86
Scheme 87
Scheme 88
Scheme 89
Scheme 90
Scheme 91
Scheme 92
- Remove side bearings from differential case.
- Install ring gear, if necessary, on differential case and tighten bolts to specification.
- Install Dummy Bearings 8398 on differential case.
- Install differential case in the housing.
- Insert Dummy Shims 8107 (1) starting point shims between both dummy bearings (4) and the housing (2).
- Install the marked bearing caps in their correct positions. Install and snug the bolts.
- Seat differential dummy bearings to each side of the housing (2) (1) with a dead-blow hammer (1) (2).
- Thread Pilot Stud C-3288-B (3) into rear cover bolt hole below ring gear.
- Attach Dial Indicator C-3339 (4) to post and position dial indicator plunger on a flat surface on a ring gear bolt head.
- Hold differential case firmly to pinion side (1) of axle housing and zero dial indicator (4).
- Hold differential case firmly (2) to the ring gear side and record dial (1) indicator reading.
- Add the dial indicator reading to the starting point shim thicknesses to determine the total shim thickness necessary to achieve zero differential end play.
- Add 0.2 mm (0.008 in) to the zero end play total. This new total represents the thickness of shims necessary to compress, or preload the new bearings when the differential is installed.
- Rotate dial indicator out of the way on pilot stud.
- Remove differential case, dummy bearings, and starting point shims from the housing.
- Install the pinion in the axle housing. Install the companion flange and establish the correct pinion rotating torque.
- Install differential case and Dummy Bearings in axle housing with a single dummy shim on the ring gear side of the axle and tighten retaining cap bolts.
- Position the dial indicator plunger on a flat surface between the ring gear bolt heads.
- Push and hold differential case toward pinion.
- Zero dial indicator face to pointer.
- Push and hold differential case to ring gear side of the housing.
- Record dial indicator reading.
- Subtract 0.05 mm (0.002 in.) from the dial indicator reading to compensate for backlash between ring and pinion gears. Add the resulting measurement to the thickness of the single starting point shim. This total is the thickness of shim required to achieve proper backlash.
- Subtract the backlash shim thickness from the total preload shim thickness. The remainder is the shim thickness required on the pinion side of the axle housing.
- Rotate dial indicator out of the way on pilot stud.
- Remove differential case, dummy bearings and dummy shim from the housing.
- Install new side bearing cones and cups on differential case.
- Install Spreader W-129-B and Adapter Plates 8142-A on the housing and spread open enough to receive differential case.
- Place the side bearing shims in the differential housing against the housing shoulder.
- Install the differential case in the housing.
- Rotate the differential case several times to seat the side bearings.
- Position the dial indicator (1) plunger against a ring gear tooth.
- Push and hold ring gear upward while not allowing the pinion gear to rotate.
- Zero dial indicator face to pointer.
- Push and hold ring gear downward while not allowing the pinion gear to rotate. Dial indicator reading should be between 0.12 mm (0.005 in.) and 0.20 mm (0.008 in.). If backlash is not within specifications transfer the necessary amount of shim thickness from one side of the differential housing to the other.
- Verify differential case and ring gear runout by measuring ring to pinion gear backlash at eight locations around the ring gear. Readings should not vary more than 0.05 mm (0.002 in.). If readings vary more than specified, the ring gear or the differential case is defective. After the proper backlash is achieved, perform the Gear Contact Pattern procedure.
GEAR CONTACT PATTERN
Gear tooth contact pattern is used to verify the correct running position of the ring and pinion gears. This will produce low noise and long gear life. Gears which are not positioned properly may be noisy and have shorten gear life.
Scheme 93
- Wipe clean each tooth of the ring gear.
- Apply gear marking compound to all of the ring gear teeth.
- Verify bearing cap bolts are torque specification.
- Apply parking brakes lightly to create at 14 N.m (10 ft. lbs.) pinion rotating torque.
- Rotate the pinion/pinion yoke 4 full revolutions in each directions.
- Read gear tooth contact pattern.
Gear contact pattern is correct. Backlash and pinion depth is correct.
Ring gear is too far away from the pinion gear, coats side toe (1) drive side heel (2). Decrease backlash by moving ring gear closer to the pinion gear using the adjusters.
Scheme 94
Ring gear is too close to the pinion gear, drive side toe (1) coast side heel (2). Increase backlash by moving ring gear away from the pinion gear using the adjusters.
Scheme 95
Ring gear is too far away from the pinion gear drive side heel (1) coast side heel (2). Decrease backlash by moving ring gear closer to the pinion gear using the adjusters.
Scheme 96
Ring gear is too close to the pinion gear, drive side toe (1) coast side toe (2). Increase backlash, by moving ring gear away from the pinion gear using the adjusters.
Scheme 97
Pinion gear is set too low. Increase pinion gear height, by increasing pinion depth shim thickness.
Scheme 98
Pinion gear is set too high. Decrease pinion height, by decreasing pinion depth shim thickness.
