
Here is how the height sensing proportioning valve
differs from a standard proportioning valve. As the
height of the rear suspension changes, the height
sensing portion of the proportioning valve changes
the split point of the proportioning valve. When the
height of the rear suspension is low, the proportion-
ing valve interprets this as extra load and the split
point of the proportioning valve is raised to a higher
pressure to allow for more rear braking. When the
height of the rear suspension is high, the proportion-
ing valve interprets this as a light load and the split
point of the proportioning valve is lowered to a lower
pressure and rear braking is reduced.
The height sensing proportioning valve regulates
the pressure by sensing the load condition of the
vehicle through the movement of the proportioning
valve actuator lever (Fig. 72). As the position of the
rear axle changes, depending on the load the vehicle
is carrying, the movement is transferred to the pro-
portioning valve. The proportioning valve adjusts the
hydraulic pressure accordingly.
The height sensing proportioning valve allows the
brake system to maintain the optimal front to rear
brake balance regardless of the vehicle load condi-
tion. Under a light load condition, hydraulic pressure
to the rear brakes is minimized. As the rear load con-
dition increases, so does the hydraulic pressure to
the rear brakes.
DIAGNOSIS AND TESTING - PROPORTIONING
VALVE (HEIGHT SENSING)
CAUTION: The use of aftermarket load leveling or
load capacity increasing devices on this vehicle is
prohibited. Using air shock absorbers or helpersprings on this vehicle will cause the height sens-
ing proportioning valve to inappropriately reduce
the hydraulic pressure to the rear brakes. This inap-
propriate reduction in hydraulic pressure potentially
could result in increased stopping distance of the
vehicle.
When a premature rear wheel skid is obtained on a
brake application, it may be an indication that the
hydraulic pressure to the rear brakes is above the
specified output from the proportioning valve. This
condition indicates a possible malfunction of the
height sensing proportioning valve, which will
require testing to verify that it is properly controlling
the hydraulic pressure allowed to the rear brakes.
Premature rear wheel skid may also be caused by
contaminated front or rear brake linings.
Prior to testing a proportioning valve for function,
check that all tire pressures are correct. Also, ensure
the front and rear brake linings are in satisfactory
condition.It is also necessary to verify that the
brakes shoe assemblies on a vehicle being
tested are either original equipment manufac-
turers (OEM) or original replacement brake
shoe assemblies meeting the OEM lining mate-
rial specification. This vehicles brake system is
not balanced for aftermarket brake shoe assem-
bly lining material.
If both front and rear brakes check OK, proceed
with the following test procedure for the height sens-
ing proportioning valve.
(1) Road test the vehicle to determine which rear
wheel brake is exhibiting premature wheel skid.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE)
(3) Remove the chassis brake tube going to the
rear brake in question at the proportioning valve.
Remove the chassis brake tube coming from the junc-
tion block at the proportioning valve (Fig. 73).
(4) Install the appropriate fittings from Pressure
Test Fittings, Special Tool 6833, into the open ports
of the proportioning valve.
(5) Install the previously removed brake lines into
the Pressure Test Fittings. Tighten all tube nuts to
17 N´m (145 in. lbs.).
(6) Install a pressure gauge from Gauge Set, Spe-
cial Tool C-4007-A into the open port on each pres-
sure test fitting. Bleed air out of hose from pressure
test fittings to pressure gauges at the pressure
gauges. Then bleed air out of the brake line being
tested at that rear wheel brake bleeder.
NOTE: Actuator rod is a linear spring and is meant
to flex by design. When rod is raised, it will have
some curvature to it.
Fig. 72 HEIGHT SENSING PROPORTIONING VALVE
1 - PROPORTIONING VALVE
2 - ACTUATOR LEVER
3 - AXLE BRACKET
4 - REAR AXLE
RSBRAKES - BASE5-49
PROPORTIONING VALVE (Continued)

(7) Remove the screw fastening the proportioning
valve actuator rod bracket to the rear axle. Raise the
actuator lever to the full-upward position and hold it
there.
(8) With the aid of a helper, apply pressure to the
brake pedal until a pressure of 6895 kPa (1000 psi) is
obtained on the proportioning valve inlet gauge.
Then, based on the type of brake system the vehicle
is equipped with and the pressure specification
shown on the following table, compare the pressure
reading on the outlet gauge to the specification. If
outlet pressure at the proportioning valve is not
within specification when required inlet pressure is
obtained, replace the proportioning valve. (Refer to 5
- BRAKES/HYDRAULIC/MECHANICAL/PROPOR-
TIONING VALVE - REMOVAL)
CAUTION: Do not attempt to adjust the height sens-
ing proportioning valve. If found to be defective,
replace the valve.(9) Remove the pressure test fittings and pressure
gauges from the proportioning valve.
(10) Install the chassis brake lines in the correct
ports of the proportioning valve. Tighten all tube
nuts to 17 N´m (145 in. lbs.).
(11) If necessary, repeat the above steps on the
remaining side of the proportioning valve which con-
trol the other rear wheel brake.
(12) Attach the actuator lever and bracket to the
rear axle.
(13) Bleed rear brakes. (Refer to 5 - BRAKES -
STANDARD PROCEDURE)
(14) Road test vehicle.
PROPORTIONING VALVE SPECIFICATIONS
WHEEL
BASEDRIVE
TRAINSALES CODE BRAKE SYSTEMSPLIT
POINTSLOPEINLET
PRESSURE
PSIOUTLET
PRESSURE
PSI
SWB FWD BRB-BGF159DISC/DRUM
W/O ANTILOCKVAR. .59 1000 PSI 675-875 PSI
REMOVAL - PROPORTIONING VALVE (HEIGHT
SENSING)
(1) Using a brake pedal depressor, move and lock
the brake pedal to a position past its first 1 inch of
travel. This will prevent brake fluid from draining
out of the master cylinder when the brake tubes are
removed from the proportioning valve.
(2) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
CAUTION: Before removing the brake tubes from
the proportioning valve, the proportioning valve and
the brake tubes must be thoroughly cleaned. This is
required to prevent contamination from entering the
proportioning valve or the brake tubes.
(3) Remove the four brake tubes from the inlet and
outlet ports of the proportioning valve (Fig. 73).
(4) Remove the two bolts attaching the proportion-
ing valve and bracket to the vehicle (Fig. 73).
(5) Slide the bracket out from under rear track bar
bracket. Lower the valve down enough to pull its
actuator rod out of the axle bracket and remove the
proportioning valve from the vehicle.
Fig. 73 PROPORTIONING VALVE MOUNTING
1 - LEFT REAR OUTLET TUBE
2 - RIGHT REAR OUTLET TUBE
3 - RIGHT REAR INLET TUBE
4 - MOUNTING BOLTS
5 - LEFT REAR INLET TUBE
5 - 50 BRAKES - BASERS
PROPORTIONING VALVE (Continued)

nects the front parking brake cable to the left rear
and intermediate cable. The intermediate cable is
connected to the right rear cable using a parking
brake cable connector.
On vehicles equipped with rear drum brakes, the
rear service brakes also act as the vehicle's parking
brakes.
Vehicles equipped with rear disc brakes use a
small duo-servo brake assembly mounted to the each
rear disc brake caliper adapter as the parking brake.
The inside of the brake rotor (hat section of drum-in-
hat style brake rotor) is used as the parking brake
drum.
DESCRIPTION - EXPORT
The parking brake system on this vehicle features
a hand-operated parking brake lever. The lever is
located between the two front seats and requires a
special front cable.
OPERATION
The automatic-adjusting feature in the foot oper-
ated parking brake lever continuously applies mini-
mal tension to the parking brake cables when the
parking brake lever is in the released position to
keep them in adjustment at all times. Due to this
feature, the parking brake cables require no periodic
adjustment.
When the parking brake lever is applied, the
cables are pulled, thus applying the brake shoes
(rear drum brakes) or parking brake shoes (rear disc
brakes) at each rear wheel.
The brake shoes are mechanically operated by an
internal lever and strut connected to the rear park-
ing brake cables.
An equalizer bracket is used at the rear end of the
front parking brake cable to distribute tension
equally to each parking brake cable.
STANDARD PROCEDURE
STANDARD PROCEDURE - PARKING BRAKE
AUTOMATIC ADJUSTER TENSION RELEASE
The parking brake lever (pedal) mechanism used
in this vehicle is designed so that the automatic
adjuster is not required to be locked out when servic-
ing the parking brake lever (pedal) or the parking
brake cables.
This parking brake lever (pedal) mechanism is
designed so that the adjuster mechanism will rotate
only half a turn when the tension is released from
the parking brake cable. This eliminates the require-
ment to lock out the automatic adjuster when servic-
ing the parking brake lever (pedal) mechanism and
cables.Use the following procedure to release the tension
from the parking brake cables and the automatic
adjuster in the parking brake lever (pedal) mecha-
nism.
(1) Grasp the exposed section of the front parking
brake cable and pull rearward on it. While holding
the park brake in this position, install a pair of lock-
ing pliers on the front parking brake cable just rear-
ward of the second body outrigger bracket (Fig. 87).
(2) Remove the left rear and intermediate parking
brake cables from the parking brake cable equalizer
(Fig. 88).
Fig. 87 Locking Out Automatic Adjuster
1 - PARK BRAKE CABLE
2 - REAR BODY OUTRIGGER BRACKET
3 - LOCKING PLIERS
Fig. 88 Parking Brake Cable Attachment To
Equalizer
1 - EQUALIZER
2 - LEFT REAR PARKING BRAKE CABLE
3 - LOCKING NUT
4 - INTERMEDIATE PARKING BRAKE CABLE
5 - FRONT PARKING BRAKE CABLE
5 - 58 BRAKES - BASERS
PARKING BRAKE (Continued)

(3) Remove the equalizer from the front parking
brake cable.
(4) Remove the locking pliers from the front park-
ing brake cable. This will allow the adjuster in the
parking brake lever (pedal) mechanism to rotate
around to its stop. This will remove the tension from
the adjuster and front park brake cable (Refer to 5 -
BRAKES/PARKING BRAKE - STANDARD PROCE-
DURE).
STANDARD PROCEDURE - PARKING BRAKE
AUTOMATIC ADJUSTER TENSION RESET
The parking brake lever (pedal) mechanism used
in this vehicle is designed so that the automatic
adjuster is not required to be locked out when servic-
ing the parking brake lever (pedal) or the parking
brake cables.
(1) Grasp the exposed section of the front parking
brake cable and pull rearward on it. While holding
the park brake in this position, install a pair of lock-
ing pliers on the front parking brake cable just rear-
ward of the second body outrigger bracket (Fig. 87).
(2) Install the equalizer on the front parking brake
cable.
(3) Install the left rear and intermediate park
brake cable in the correct location on the parking
brake cable equalizer (Fig. 88).
(4) Remove the locking pliers from the front park-
ing brake cable. This will allow the adjuster in the
park brake lever (pedal) mechanism to tension the
park brake cables.
(5) Apply and release the parking brake lever
(pedal) one time. This will seat the parking brake
cables and allow the auto adjuster in the parking
brake lever (pedal) mechanism to correctly tension
the parking brake cables.
CABLES - PARKING BRAKE
REMOVAL
REMOVAL - PARKING BRAKE CABLE (FRONT)
(1) Raise vehicle on jackstands or centered on a
hoist. (Refer to LUBRICATION & MAINTENANCE/
HOISTING - STANDARD PROCEDURE).
(2) Manually release the automatic self-adjusting
mechanism tension of the parking brake lever (pedal)
assembly. (Refer to 5 - BRAKES - STANDARD PRO-
CEDURE).
(3) Remove the intermediate and left rear park
brake cable from the park brake cable equalizer (Fig.
89).
(4) Remove the front park cable housing retainer
from body outrigger bracket (Fig. 90). Cable isremovable by sliding a 14 mm box wrench over cable
retainer and compressing the three retaining fingers.
Alternate method is to use an aircraft type hose
clamp and screwdriver.
(5) Lower vehicle.
(6) Remove the left front door sill molding.
(7) Remove the left front kick panel for access to
the park brake cable and park brake pedal assembly.
(8) Lift floor mat for access to park brake cable
and floor pan. Pull the seal and the park brake cable
(Fig. 91) out of the floor pan of vehicle.
Fig. 89 Park Brake Cable Attachment To Equalizer
1 - EQUALIZER
2 - LEFT REAR PARKING BRAKE CABLE
3 - LOCKING NUT
4 - INTERMEDIATE PARKING BRAKE CABLE
5 - FRONT PARKING BRAKE CABLE
Fig. 90 Front Park Brake Cable Attachment To Body
1 - CABLE HOUSING RETAINER
2 - BODY OUTRIGGER BRACKET
3 - PUSH WRENCH OVER END OF RETAINER HERE
4 - FRONT PARK BRAKE CABLE
RSBRAKES - BASE5-59
PARKING BRAKE (Continued)

(9) Pull parking brake cable strand end forward
and disconnect button from clevis. Tap cable housing
end fitting out of pedal assembly bracket.
(10) Remove cable retainer from the parking brake
lever (pedal) assembly bracket.
(11) Pull front parking brake cable assembly out of
vehicle through hole in floor pan.
REMOVAL - PARKING BRAKE CABLE
(INTERMEDIATE)
(1) Raise the vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE).
(2) Manually lock out the automatic self-adjusting
mechanism tension of the parking brake lever (pedal)
assembly. (Refer to 5 - BRAKES - STANDARD PRO-
CEDURE). Once the cable is released from the equal-
izer, do not remove the locking pliers until
reinstallation of the cable is complete.
(3) Remove the intermediate parking brake cable
from the parking brake cable equalizer (Fig. 92).
(4) Remove the locking nut securing the interme-
diate cable housing to the side bracket on the frame
rail (Fig. 92).
(5) Remove the intermediate parking brake cable
from the cable connector attaching it to the right
rear parking brake cable (Fig. 93). Remove the lock-
ing nut securing the intermediate cable housing to
the side bracket on the frame rail (Fig. 93).
(6) If the vehicle is a short-wheel-base model, it
will be necessary to loosen and lower the fuel tank
far enough to remove the intermediate parking brakecable. (Refer to 14 - FUEL SYSTEM/FUEL DELIV-
ERY/FUEL TANK - REMOVAL).
(7) Remove the intermediate parking brake cable
from the side brackets and vehicle.
REMOVAL - PARKING BRAKE CABLE (RIGHT
REAR)
(1) Raise vehicle on jackstands or centered on a
hoist. (Refer to LUBRICATION & MAINTENANCE/
HOISTING - STANDARD PROCEDURE).
(2) Remove rear tire and wheel assembly.
(3) Remove rear brake drum from the rear wheel
of the vehicle requiring service to the rear park
brake cable.
Fig. 91 Front Park Brake Cable At Floor Pan
1 - PARK BRAKE PEDAL ASSEMBLY
2 - PARK BRAKE PEDAL
3 - CARPET
4 - FRONT PARK BRAKE CABLE
5 - SEAL
6 - FLOOR PAN
Fig. 92 Parking Brake Cable Attachment To
Equalizer
1 - EQUALIZER
2 - LEFT REAR PARKING BRAKE CABLE
3 - LOCKING NUT
4 - INTERMEDIATE PARKING BRAKE CABLE
5 - FRONT PARKING BRAKE CABLE
Fig. 93 Intermediate Cable Attachment To Right
1 - RIGHT REAR PARKING BRAKE CABLE
2 - LOCKING NUT
3 - INTERMEDIATE PARKING BRAKE CABLE
5 - 60 BRAKES - BASERS
CABLES - PARKING BRAKE (Continued)

(4) Create slack in the rear parking brake cables
by locking out the automatic adjuster as described
here. Grasp an exposed section of front parking
brake cable near the equalizer and pull down on it.
At this time install a pair of locking pliers on the
cable just rearward of the second body outrigger
bracket (Fig. 94).
(5) Disconnect the right rear parking brake cable
from the connector on the intermediate cable (Fig.
95).
(6) To remove the right parking brake cable hous-
ing from the body bracket, slide a 14 mm box end
wrench over the end of cable retainer to compress the
retaining fingers (Fig. 96). The alternate methodusing an aircraft type hose clamp will not work on
the right side of the vehicle.
(7) Remove the brake shoes from the brake sup-
port plate. (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/BRAKE PADS/SHOES - REMOVAL).
(8) Disconnect parking brake cable from parking
brake actuator lever.
(9) Remove the parking brake cable housing
retainer from the brake support plate using a 14mm
wrench to compress the retaining fingers (Fig. 97).
Remove the cable.
Fig. 94 Locking Out Automatic Adjuster
1 - PARK BRAKE CABLE
2 - REAR BODY OUTRIGGER BRACKET
3 - LOCKING PLIERS
Fig. 95 Right Rear Cable Connection To
Intermediate Cable
1 - RIGHT REAR PARKING BRAKE CABLE
2 - LOCKING NUT
3 - INTERMEDIATE PARKING BRAKE CABLE
Fig. 96 Right Park Brake Cable Removal From Body
Bracket
1 - RIGHT REAR BODY BRACKET
2 - PARK BRAKE CABLE
3 - 14MM WRENCH
4 - LEAF SPRING AND BRACKET
Fig. 97 Removing Park Brake Cable From Brake
Support Plate
1 - PARK BRAKE CABLE RETAINER
2 - PARK BRAKE CABLE
3 - 14MM BOX WRENCH
4 - BRAKE SUPPORT PLATE
RSBRAKES - BASE5-61
CABLES - PARKING BRAKE (Continued)

REMOVAL - PARKING BRAKE CABLE (LEFT
REAR)
(1) Raise vehicle on jackstands or centered on a
hoist. (Refer to LUBRICATION & MAINTENANCE/
HOISTING - STANDARD PROCEDURE).
(2) Remove rear tire and wheel assembly.
(3) Remove rear brake drum from the rear wheel
of the vehicle requiring service to the rear park
brake cable.
(4) Create slack in rear park brake cables by lock-
ing out the automatic adjuster as described here.
Grasp an exposed section of front park brake cable
near the equalizer and pull down on it. Then install
a pair of locking pliers on the cable just rearward of
the second body outrigger bracket (Fig. 98).
(5) Disconnect the left rear parking brake cable
from the parking brake cable equalizer (Fig. 99).
(6) To remove parking brake cable housing from
the body bracket, slide a 14 mm box end wrench over
retainer end compressing the three fingers (Fig. 100).
Alternate method is to use an aircraft type hose
clamp.
(7) Remove the brake shoes from the brake sup-
port plate. (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/BRAKE PADS/SHOES - REMOVAL).
(8) Disconnect parking brake cable from parking
brake actuator lever.(9) Remove the parking brake cable housing
retainer from the brake support plate using a 14mm
wrench to compress the retaining fingers (Fig. 101).
Fig. 98 Locked Out Park Brake Automatic Adjuster
1 - PARK BRAKE CABLE
2 - REAR BODY OUTRIGGER BRACKET
3 - LOCKING PLIERS
Fig. 99 Parking Brake Cables At Equalizer
1 - EQUALIZER
2 - LEFT REAR PARKING BRAKE CABLE
3 - LOCKING NUT
4 - INTERMEDIATE PARKING BRAKE CABLE
5 - FRONT PARKING BRAKE CABLE
Fig. 100 Parking Brake Cable Removal From Body
Bracket
1 - LEFT REAR PARK BRAKE CABLE
2 - BODY BRACKET
3 - LEAF SPRING MOUNTING BRACKET
4 - CABLE RETAINER
5 - 14MM BOX WRENCH
5 - 62 BRAKES - BASERS
CABLES - PARKING BRAKE (Continued)

INSTALLATION
INSTALLATION - PARKING BRAKE CABLE
(FRONT)
(1) Pass front parking brake cable assembly
through hole in floor pan from the inside of the vehi-
cle.
(2) Pass cable strand button through the hole in
the lever (pedal) assembly bracket.
(3) Install cable retainer onto the park brake cable
and then install cable retainer into pedal assembly
bracket.
(4) Install the end of the park brake cable into the
retainer previously installed into the park brake
pedal bracket.
(5) Install cable strand button into the clevis on
the park brake pedal mechanism.
(6) Install the front park brake cable floor pan seal
into hole in floor pan. Seal is to be installed so the
flange on the seal is flush with the floor pan (Fig.
91). Fold carpeting back down on floor.
(7) Raise vehicle.
(8) Insert brake cable and housing into body out-
rigger bracket making certain that housing retainer
fingers lock the housing firmly into place (Fig. 90).
(9) Manually reset the automatic self-adjusting
mechanism tension of the parking brake lever (pedal)
assembly. (Refer to 5 - BRAKES - STANDARD PRO-
CEDURE).
(10) Assemble the park brake cables onto the park
brake cable equalizer (Fig. 89).
(11) Lower vehicle and apply the park brake pedal
1 time. This will seat the parking brake cables.
INSTALLATION - PARKING BRAKE CABLE
(INTERMEDIATE)
(1) Install the ends of the park brake cables
through the frame rails and into the side brackets.
(2) Install the locking nuts at each end of the cable
and securely tighten (Fig. 92) (Fig. 93).
(3) If the vehicle is a short-wheel-base model, it
will be necessary to reinstall the fuel tank to its nor-
mal mounting position. (Refer to 14 - FUEL SYS-
TEM/FUEL DELIVERY/FUEL TANK -
INSTALLATION).
(4) Install the intermediate parking brake cable on
the cable connector at the right rear parking brake
cable (Fig. 93).
(5) Install the intermediate park brake cable on
the cable equalizer (Fig. 92).
(6) Remove the locking pliers from the front park
brake cable. This will activate the automatic adjuster
and correctly adjust the parking brake cables.
(7) Install and position the foam collar on the
parking brake cable to prevent it from rattling
against the vehicle's floor.
(8) Lower the vehicle and apply the park brake
pedal 1 time, this will seat the park brake cables.
INSTALLATION - PARKING BRAKE CABLE
(RIGHT REAR)
(1) Install the rear parking brake cable in the
brake support plate. Insert cable housing retainer
into brake support plate making certain that cable
housing retainer fingers lock the housing and
retainer firmly into place.
(2) Attach the parking brake cable onto the park-
ing brake actuator lever.
(3) Install the brake shoes on the rear brake sup-
port plate. (Refer to 5 - BRAKES/HYDRAULIC/ME-
CHANICAL/BRAKE PADS/SHOES -
INSTALLATION).
(4) Insert cable housing retainer into body outrig-
ger bracket making certain that cable housing
retainer fingers lock the housing firmly into place.
(5) Connect the right rear parking brake cable to
the connector on the intermediate parking brake
cable (Fig. 95).
(6) Install the brake drum, then the wheel and tire
assembly.
(7) Remove the locking pliers from the front park
brake cable. This will automatically adjust the park
brake cables.
(8) Lower the vehicle.
(9) Apply and release park brake pedal 1 time.
This will seat the park brake cables.
Fig. 101 Removing Parking Brake Cable From Brake
Support Plate
1 - PARK BRAKE CABLE RETAINER
2 - PARK BRAKE CABLE
3 - 14MM BOX WRENCH
4 - BRAKE SUPPORT PLATE
RSBRAKES - BASE5-63
CABLES - PARKING BRAKE (Continued)