Page 145 of 2158
Fig. 33 Gear Teeth Contact Patterns
3 - 44 REAR SUSPENSION AND AXLESJ
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TRAC-LOK DIFFERENTIAL
OPERATION
In a conventional differential, the torque applied to
the ring gear is transmitted to the axle shafts through
the differential gears. During normal operation, the
torque transmitted to each wheel is equal at all times.
However, if one wheel spins, the opposite wheel will
generate only as much torque as the spinning wheel.
In the Trac-Lok differential, part of the ring gear
torque is transmitted through clutch packs. The clutch
packs contain multiple disc. The clutch will have radial
grooves on the plates, and concentric grooves on the
discs or bonded fiber material which is smooth.
In operation, the Trac-Lok clutches are engaged by
two concurrent forces. The first being preload force ex-
erted through Belleville spring washers. The second is
from separating forces generated by the side gears (Fig.
1).
The Trac-Lok design provides the normal differential
action needed for turning corners. It also provides for
the transmission of equal torque to both wheels when
driving straight ahead. When one wheel loses traction,
the clutch packs transfer torque to the wheel having the
most traction. Trac-lok differentials resist wheel spin on
bumpy roads. It also provides more pulling power when
one wheel loses traction. Pulling power is continuous
until both wheels lose traction. If both wheels slip due
to unequal traction, Trac-Lok operation is normal. In ex-
treme cases of differences of traction, the wheel with
the least traction may spin. This occurs after the Trac-
Lok has transferred as much torque as possible to the
non-spinning wheel.
NOISE DIAGNOSIS
If chatter occurs when turning corners, the most
probable cause is incorrect or contaminated lubri-
cant. Before removing the Trac-Lok unit for repair,
drain, flush and refill the axle with the specified lu-
bricant. Refer to Lubricant change in this Group.
A container of Trac-Lok Lubricant (friction modi-
fier) should be added after.
Vehicles with a limited slip differential should be
road tested by making 10 to 12 slow figure-eight
turns. This maneuver will pump the lubricant
through the clutch discs.
Refer to Group 0, Lubrication and Maintenance for
additional information.
DIFFERENTIAL TEST
WARNING: WHEN SERVICING VEHICLES WITH A
LIMITED SLIP DIFFERENTIAL DO NOT USE THE EN-
GINE TO TURN THE AXLE AND WHEELS. BOTH
REAR WHEELS MUST BE RAISED AND THE VEHI-
CLE SUPPORTED. A LIMITED SLIP AXLE CAN EX-
ERT ENOUGH FORCE (IF ONE WHEEL IS IN
CONTACT WITH THE SURFACE) TO CAUSE THE
VEHICLE TO MOVE.
The differential can be tested without removing the
differential case by measuring rotating torque. Make
sure brakes are not dragging during this measure-
ment.
(1) Engine off, transmission in neutral, and park-
ing brake off.
(2) Place blocks in front and rear of both front
wheels.
(3) Jack up one rear wheel until it is completely off
the ground.
(4) Remove wheel and bolt special tool to studs.
Fig. 1 Limited Slip Differential OperationÐBoth
Wheels Driving
JREAR SUSPENSION AND AXLES 3 - 45
Page 147 of 2158
(5) Use torque wrench on Special Tool 6790 to ro-
tate wheel and read rotating torque (Fig. 2).
(6) If rotating torque is less than 22 Nzm (30 ft.
lbs.) or more than 271 Nzm (200 ft. lbs.) on either
wheel the unit should be service.
DIFFERENTIAL OVERHAUL
The Trac-Lok differential components are illus-
trated in (Fig. 3). Refer to this illustration during re-
pair service.
DISASSEMBLY
Service to the Trac-Lok differential requires the
use of Tool Set C-4487 (J-23781). Refer to Model 35
Axle section in this Group for Differential Removal
and Installation.
(1) Clamp one axle shaft in a vise equipped with
soft jaws (Fig. 4).
Fig. 3 Trac-Lok Differential Components
Fig. 2 Trac-Loc Test
Fig. 4 Axle Shaft As Holding Fixture
3 - 46 REAR SUSPENSION AND AXLESJ
Page 148 of 2158
(2) Position the differential case on the axle shaft
(Fig. 5). Place shop towels under the differential to
avoid damage during removal of the ring gear (Fig.
5).
(3) Remove and discard the ring gear bolts. Tap
the ring gear with a rawhide or plastic mallet and re-
move (Fig. 6).
(4) Remove the pinion gear mate shaft lock screw
(Fig. 7).
(5) Remove the pinion gear mate shaft with a drift
and hammer (Fig. 8).
(6) Install and lubricate Step Plate C-4487-1 (Fig.
9).
(7) Assemble Threaded Adapter C-4487-3 into top
side gear. Thread forcing Screw C-4487-2 into
adapter until it becomes centered in adapter plate.
Fig. 7 Mate Shaft Lock Screw
Fig. 8 Mate Shaft Removal
Fig. 9 Step Plate Tool Installation
Fig. 5 Differential Case On Shaft
Fig. 6 Ring Gear Removal
JREAR SUSPENSION AND AXLES 3 - 47
Page 149 of 2158
(8) Position a small screw driver in slot of
Threaded Adapter C-4487-3 (Fig. 10 to prevent
adapter from turning.
(9) Tighten forcing screw tool enough to relieve
clutch pack tension. Remove both pinion thrust
washers (Fig. 11).
(10) Loosen the forcing screw tool until the clutch
pack tension is relieved.
(11) Insert Turning Bar C-4487-4 in case. Rotate
case with tool until pinion gears can be removed (Fig.
12).(12) Remove top side gear and clutch pack. Keep
plates in correct order during removal (Fig. 13).
(13) Remove case from fixture. Remove remaining
clutch pack.
(14) Remove clutch pack retaining clips. Mark each
clutch pack for installation reference.
CLEANING AND INSPECTION
(1) Clean all components in cleaning solvent. Dry
components with compressed air.
Fig. 10 Threaded Adapter Installation
Fig. 11 Remove Pinion Thrust Washer
Fig. 12 Pinion Gear Removal
Fig. 13 Side Gear & Clutch Disc Removal
3 - 48 REAR SUSPENSION AND AXLESJ
Page 150 of 2158

(2) Inspect clutch pack plates for wear, scoring or
damage. Replace both clutch packs if any one compo-
nent in either pack is damaged.
(3) Inspect side and pinion gears. Replace any gear
that is worn, cracked, chipped or damaged.
(4) Inspect differential case and pinion shaft. Re-
place if worn or damaged.
PRESOAK PLATES AND DISC
Plates and dics with fiber coating (no groves or
lines) must be presoaked in Friction Modifier before
assembly. Soak plates and discs for a minimum of 20
minutes. Add remaining Friction Modifier to differen-
tial after assembly.
ASSEMBLY
(1) The clutch discs are replaceable as complete
sets only. If one clutch disc pack is damaged, both
packs must be replaced. Lubricate each component
with gear lubricant before assembly and installation.
(2) Assemble the clutch discs into packs and secure
disc packs with retaining clips (Fig. 14).
(3) Position assembled clutch disc packs on the
side gear hubs.
(4) Position case on axle fixture.
(5) Install clutch pack and side gear in lower bore
(Fig. 15). Be sure clutch pack retaining clips remain
in position and are seated in the case pockets.
(6) Install lubricated Step Plate C-4487-1 on first
clutch pack (Fig. 16).
(7) Install the upper side gear and clutch disc pack
(Fig. 16).
(8) Hold assembly in position. Insert Threaded
Adapter C-4487-3 into top side gear, insert forcing
Screw C-4487-2.(9) Tighten forcing screw tool to compress clutch
discs.
(10) Install pinion gears. Rotate case with Turning
Bar C-4487-4. Make sure holes of pinion mate gears
are aligned with case.
(11) Tighten forcing screw to compress the
Belleville plates. Lubricate and install pinion gear
thrust washers with a small screw driver.
(12) Install pinion gear mate shaft ( align holes in
shaft and case).
(13) Install the pinion mate shaft lock screw finger
tight.
If replacement gears and thrust washers were
installed, it is not necessary to measure the
gear backlash. Correct fit is due to close ma-
chining tolerances during manufacture.
Fig. 14 Clutch Disc Pack
Fig. 15 Clutch Discs & Lower Side Gear Installation
Fig. 16 Upper Side Gear & Clutch Disc Pack
Installation
JREAR SUSPENSION AND AXLES 3 - 49
Page 151 of 2158
(14) Invert the differential case and start two ring
gear bolts. This will provide case-to-ring gear bolt
hole alignment.
(15) Install new ring gear bolts and alternately
tighten to 95-122 Nzm (70-90 ft. lbs.) torque (Fig. 17).
(17) Lubricate all differential components with hy-
poid gear lubricant.
Fig. 17 Ring Gear Bolt Installation
3 - 50 REAR SUSPENSION AND AXLESJ
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AXLE SPECIFICATIONS
MODEL 35 AXLE
Axle Type...............................Semi-Floating Hypoid
Lubricant................SAE Thermally Stable 80W-90
Lubricant Trailer Tow.............Synthetic 75W-140
Lube Capacity..............................1.66 L (3.50 pts.)
Axle Ratio................................3.07, 3.55, 3.73, 4.10
Differential
Bearing Preload ............................0.1 mm (0.004 in.)
Side Gear Clearance ............0-0.15 mm (0-0.006 in.)
Ring Gear
Diameter .......................................19.2 cm (7.562 in.)
Backlash.........................0-0.15 mm (0.005-0.008 in.)
Pinion Std. Depth...................96.8 mm (3.813 in.)
Pinion Bearing Preload
Original Bearing ....................1-2Nzm (10-20 in. lbs.)
New Bearing .......................1.5-4Nzm (15-35 in. lbs.)
8 1/4 AXLE
Axle Type................................Semi-floating, hypoid
Lubricant...............................................SAE 75W-90
Lube Capacity................................2.08 L (4.4 pts.)
Axle Ratios.........................................3.07 3.55 4.10
Differential
Side Gear Clearance ..................0.12 mm (0.005 in.)
Case Flange Runout ..................0.07 mm (0.003 in.)
Bearing Preload ...........................95 Nzm (70 ft. lbs.)
Ring Gear
Diameter .......................................20.95 cm (8.25 in.)
Backlash....................0.12-0.20 mm (0.005-0.008 in.)
Runout .......................................0.127 mm (0.005 in.)
Pinion Bearing
Preload ....................................1-2 Nzm (10-20 in.lbs.)
TORQUE SPECIFICATIONS
XJ REAR SUSPENSION COMPONENTS
DESCRIPTION ................................................TORQUE
Shock Absorber
Upper Bolt ...................................23 Nzm (17 ft. lbs.)
Lower Nut ....................................62 Nzm (46 ft. lbs.)
Stabilizer Bar
Clamp Bolt ...................................54 Nzm (40 ft. lbs.)
Link Upper Bolt ............................12 Nzm (9 ft. lbs.)
Link Lower Nut ..........................74 Nzm (55 ft. lbs.)
Spring
U-Bolt Nut ...................................70 Nzm (52 ft. lbs.)
Front Pivot Bolt ......................148 Nzm (109 ft. lbs.)
Upper Shackle Bolt .................148 Nzm (109 ft. lbs.)
Lower Shackle Bolt ...................108 Nzm (80 ft. lbs.)
YJ REAR SUSPENSION COMPONENTS
DESCRIPTION ................................................TORQUE
Shock Absorber
Upper Nut ....................................61 Nzm (45 ft. lbs.)
Lower Nut ....................................61 Nzm (45 ft. lbs.)
Track Bar
Frame Bracket Nut.................142 Nzm (105 ft. lbs.)
Axle Bracket Nut ....................142 Nzm (105 ft. lbs.)Spring
U-Bolt Nut .................................122 Nzm (90 ft. lbs.)
Rear Shackle Bolts..................136 Nzm (100 ft. lbs.)
Front Pivot Bolt ......................142 Nzm (105 ft. lbs.)
MODEL 35 AXLE
DESCRIPTION ................................................TORQUE
Fill Hole Plug...........................34 Nzm (25 ft. lbs.)
Diff. Cover Bolt........................41 Nzm (30 ft. lbs.)
Bearing Cap Bolt.....................77 Nzm (57 ft. lbs.)
Pinion Nut...............292-427 Nzm (215-315 ft. lbs.)
Ring Gear Bolt.............95-122 Nzm (70-90 ft. lbs.)
RWAL/ABS Sensor Bolt.........24 Nzm (18. ft. lbs.)
8 1/4 AXLE
DESCRIPTION ................................................TORQUE
Diff. Cover Bolt........................47 Nzm (35 ft. lbs.)
Bearing Cap Bolt.....................95 Nzm (70 ft. lbs.)
Pinion Nut.............................285 Nzm (210 ft. lbs.)
Ring Gear Bolt.........................95 Nzm (70 ft. lbs.)
RWAL/ABS Sensor Bolt.........24 Nzm (18. ft. lbs.)
JREAR SUSPENSION AND AXLES 3 - 51