Chrysler RAM TRUCK 2500 1994 Service Manual page 151

3 - 44 REAR SUSPENSION AND AXLE
TRAC-LOK/POWER-LOK DIFFERENTIAL
SERVICE INFORMATION
Trac-Lok differential is available on 9 1/4 and
Model 60 axles. Power-Lok differential is available on
Model 70 and 80 axles.
In a conventional differential, torque applied to the
ring gear is transmitted to the axle shafts through
differential gears. During normal operation, the
torque transmitted to each wheel is equal at all
times. However, i f one wheel spins, the opposite
wheel will generate only as much torque as the spin­
ning wheel.
In the Trac-Lok/Power/Lok differential, part of the
ring gear torque is transmitted through clutch packs.
The clutch packs contain multiple disc clutches
which have radial grooves on the plates and concen­
tric grooves on the discs.
In operation, the Trac-Lok/Power-Lok clutches are
engaged by two concurrent forces. The first being
preload force exerted through dished spring washers
contained i n the clutch packs. The second from sepa­
rating forces generated by the side gears as torque is
applied through the ring gear (Fig. 1).
The Trac-lok design provides differential action
needed for turning corners and for driving straight
ahead. However, when one wheel looses traction, the
clutch packs transfer additional torque to the wheel
having the most traction. Trac-lok differentials resist
wheel spin on bumpy roads and provide more pulling
power when one wheel looses traction. Pulling power
is provided continuously until both wheels loose trac­
tion. I f both wheels slip due to unequal traction,
Trac-lok operation is normal. I n extreme cases of dif­
ferences of traction, the wheel with the least traction
may spin.
NOISE DIAGNOSIS
I f a noise 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 i n this Group.
A container of Trac-Lok Lubricant (friction modi­
fier) should be added after repair service or a lubri­
cant change.
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 to eliminate a possible chat­
ter or pop noise complaint.
Refer to Group 0, Lubrication and Maintenance for
additional information.
TRAC-LOK/POWER-LOK DIFFERENTIAL T E S T
WARNING: WHEN SERVICING V E H I C L E S WITH A
LIMITED S L I P D I F F E R E N T I A L DO NOT U S E T H E E N -
RING
GEAR
DRIVE
PINION
PINION GEAR
J9303-15
Fig. 1 Limited Slip Differential Operation—Both
Wheels Driving
GINE TO TURN T H E A X L E AND W H E E L S . BOTH
R E A R W H E E L S MUST BE RAISED AND T H E VEHI­
C L E S U P P O R T E D . A LIMITED S L I P A X L E CAN E X ­
E R T ENOUGH F O R C E (IF ONE W H E E L IS IN
CONTACT WITH T H E S U R F A C E ) TO C A U S E T H E
V E H I C L E 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 i n front and rear of both front
wheels.
(3) Jack up one rear wheel until i t is completely off
the ground.
(4) Remove wheel and bolt Special Tool 6790 for
Trac-Lok or Special Tool for Power-Lok to studs.
(5) Use torque wrench on special tool to rotate
wheel and read rotating torque (Fig. 2,3).
(6) I f rotating torque is less than 22 N-m (30 ft.
lbs.) or more than 271 N-m (200 ft. lbs.) on either
wheel the unit should be service.
LUBRICANTS
The lubricant recommended for Trac-Lok/Power-
Lok differential is API grade GL 5. A container of
Trac-Lok Lubricant (friction modifier) should be
added after service.