BENDIX ATR-2 ANTILOCK TRACTION VALVE User guide

FIGURE 1 - ATR-2™ANTILOCK TRACTION RELAY VALVE
DESCRIPTION
TheATR-2™antilock tractionrelayvalveis aspecialized air
brake valve developed for use on Bendix antilock/traction
equippedtractorsonly.
Itisessentially threeseparatevalvesworking incombination
in a single housing. An R-14™style service relay valve is
thebase valveand isfittedwithamodified covercontaining
abobtailtractorbrake proportioningvalve(referenceBendix
Service Data Sheet SD-03-1067) and a traction control
solenoid. TheATR-2™valve contains both air and electric
components and provides both the service braking and
traction control (differential braking) functions. A Bendix
antilock traction controller can be mounted to theATR-2™
valve or a cover plate can be installed and the antilock
controllermountedelsewhereonthe vehicle.
TheATR-2™valve replacesthestandard relayvalveused to
control the rear axle service brakes and performs the
standardrelayfunctionduringtractor-traileroperation. During
tractor bobtail operation, theATR-2™valve reduces brake
application pressure to the lighter rear axle(s) brakes to
improve vehicle controllability and minimize rear axle(s)
wheel skid before antilock is required. TheATR-2™valve
provides added vehicle braking control and reduces the
number of times antilock is actually needed.
Likethestandardrelayvalve itreplaces, theATR-2™valve
and its attached antilock controller is normally mounted
near the service brakes it serves. A mounting bracket,
furnished with the valve, permits either frame or cross
membermounting. All airconnections ontheATR-2™valve
are identified with cast, embossed letters for ease of
identification and installation. The letter identification and
airlineconnections areshown belowfor reference.
ATR-2™VALVE
AIRCONNECTION EMBOSSED IDENT.
Supply (to reservoir) SUP
Delivery (to brake chamber) DEL
Service (to brake valve rear delivery) SER
Control (to delivery of trailer supply valve) CON
TheATR-2™valveis partoftheR-12™familyof relayvalves
which includes the R-12™, R-14™, BP-R1™,AR-1™valves.
Theinternalcomponents ofthe relay portionof allofthese
valvesareinterchangeablewiththeR-12™valveandtherefore
thesame basiccomponents areusedtoserviceall ofthem.
TheATR-2™valve isavailable withvariouscrackpressures
toaccommodatespecificapplications,howeverthestandard
is 4 psi.
NOTE: AN OPTIONAL COVER PLATE IS INSTALLED OVER THE TOP WHEN THE
ATR-2™VALVE IS MOUNTED REMOTE FROM THE ANTILOCK TRACTION CONTROLLER
CONTROLLER OR COVER
PLATE MOUNTING HOLES:
SEE NOTE
MOUNTING
BRACKET
BODY
SUPPLY PORT
BOBTAIL
PROPORTIONING
VALVING
SERVICE PORT
CONTROL PORT
DELIVERY PORT (4)
2 PIN SOLENOID
CONNECTOR
SUPPLY
PORT
COVER
TRACTION CONTROL
SOLENOID
®
SD-13-4812
Bendix®ATR-2™AntiLock Traction Relay Valve

2
OPERATION
GENERAL
Because the ATR-2™valve is actually a relay valve, the
followingdescription ofoperation referstoitsfunctionin the
vehicle’s air brake system and does not address all of the
separate antilock components and their operation. For a
description of antilock operation refer to the appropriate
ServiceDataSheet coveringthe electroniccontroller used
withtheATR-2™valve.
INITIAL CHARGING
During the initial build up of tractor system air pressure,
reservoirairflows intothe supply portand throughinternal
body and cover passages to the blend back piston and
fromthere tothesupplyofthe normallyclosed(NC)traction
controlsolenoid. Whensufficient airpressure isapplied to
the blend back piston, it moves against the resistance of
its spring until it comes to rest against the service piston.
Activating the trailer supply valve (dash control with red
octagonal button), simultaneously charges the trailer and
the ATR-2™valve’s control port. Air entering the ATR-2™
valve’s control causes the proportioning piston to move
toward its stop in the cover. The integral inlet and exhaust
valveiscarriedalongwiththepistonuntilitseatsandseals
the exhaust passage. Continued movement of the
proportioning piston opens the inlet seat. With the tractor
and trailer air system fully charged the vehicle may be
operated.
SERVICE BRAKES APPLYING - TRACTOR/
TRAILER COMBINATION (FIGURE 4)
Brakeapplication airenters theATR-2™valve’sserviceport
and is conducted to the single check valve. The check
valvediaphragm flexesin responseto applicationpressure
and seals the passage to the open exhaust of the traction
solenoid. Airflowsthrough theservice pistonthen through
thecenter ofboth theblend backand proportioningpistons
to the inlet and exhaust valve. Flowing around the inlet
valve,application airmoves throughapassageinthe cover
to the top of the service relay piston. In response to air
pressure, the relay piston moves into contact with the
exhaust portion of its inlet and exhaust valve. With the
exhaustpassage sealed,continuedmovement ofthepiston
unseats the inlet portion of the inlet and exhaust valve,
allowingsupply airfromthereservoirto flowout theATR-2™
valve’sdeliveryports tothe brakechambers.
SERVICE BRAKES HOLDING - TRACTOR/
TRAILER COMBINATION (FIGURE 5)
The air pressure being delivered to the brake chambers is
alsopresentbeneaththerelaypiston. Whentheairpressure
above and below relay piston is equal, the piston moves
slightly allowing the inlet valve to return to its seat. The
exhaust valve remains closed. With both the inlet and
exhaustvalvesclosed, airpressure inthe brakechambers
is held stable and neither increases nor decreases.
SERVICE BRAKES RELEASING - TRACTOR/
TRAILER COMBINATION (FIGURE 6)
Whenthebrake applicationis released,air fromabovethe
relay piston, flows back through the proportioning, blend
back and service pistons to the foot brake valve and is
exhausted. As air pressure is reduced above the relay
piston, pressure beneath it lifts the piston away from the
exhaust valve and opens the exhaust passage. Air from
the service brake chambers returns to the ATR-2™valve
and flows out the open exhaust.
ATR-2™ANTILOCK
TRACTION RELAY
CONTROLLER
FIGURE 2 - ANTILOCK TRACTION ASSEMBLY
TRACTION CONTROL
SOLENOID
SUPPLY
SERVICE
DOUBLE
CHECK
VALVE
DELIVERY
EXHAUST
RELAY PISTON
INLET-EXHAUST
VALVE
BLEND
BACK
PISTON
SOLENOID
CONNECTOR
FIGURE 3 - SECTIONAL ATR-2™ANTILOCK TRACTION ASSY.
INLET-EXHAUST
VALVE
CONTROL
PROPORTIONING
PISTON

3
FIGURE 4 - SERVICE BRAKE APPLICATION
FIGURE 5 - SERVICE BRAKES HOLDING
CONTROLLER TRACTION SOLENOID
CHECK VALVE
RELAY PISTON
INLET EXHAUST
MODULATOR
SERVICE BRAKE
REAR AXLE
RESERVOIR
TRAILER
SUPPLY
PROPORTIONING
PISTON
INLET EXHAUST
CONTROLLER
BRAKE
VALVE
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
INLET EXHAUST
SERVICE BRAKE
REAR AXLE
RESERVOIR
TRAILER SUPPLY
PROPORTIONING
PISTON
INLET EXHAUST
TRACTION SOLENOID
MODULATOR

4
SERVICE APPLICATION - BOBTAIL TRACTOR
(FIGURE 7)
Whenthetrailersupplyvalve(dashcontrolwithredoctagonal
button) is activated to disconnect the trailer, air in the
ATR-2™valve’s control port and trailer supply line is
exhaustedto atmosphere. Duringbobtail tractoroperation,
serviceapplicationairenters theATR-2™valve’sserviceport
and is conducted to the single check valve. The check
valvediaphragm flexesin responseto applicationpressure
and seals the passage to the open exhaust of the traction
solenoid. Application air passes through the blend back
pistonand exertsaforceonthe fulleffectivediameterofthe
piston. The blend back piston remains stationary at
applicationpressures belowapproximately 80psi because
ofopposingreservoir airacting onthelarge diameter.
Application air flowing through the blend back piston also
exerts a force on the small diameter of the proportioning
pistonwhilesimultaneously flowingthrough thecenter ofit
on its way to the inlet and exhaust valve. Once past the
inletandexhaust valve,service airpressureexerts aforce
onthelargerdiameterendof theproportioningpiston, which
opposes the air pressure and spring force exerted on the
otherend. Theproportioning pistoninletvalveremainsopen
until a preset, initial application pressure has reached the
relay piston assuring that the foundation brake shoes are
brought into contact with the drum. As service pressure
begins to exceed the preset initial application, the
proportioningpiston willhave movedsufficiently toclose its
inletvalvewithout openingthe exhaust.
Theinletremains closed,preventing additionalair delivery
to the relay piston and a subsequent increase in brake
chamber pressure, until service application pressure
exceedsapproximately30psi. Serviceapplicationsabove
this pressure will result in a proportioned increase of the
preset initial brake application to the tractor’s rear brakes.
Proportioningoccursduetothe differencein effectivearea
on each end of the proportioning piston. Tractor rear axle
brake proportioning will occur for all service applications
betweenapproximately30 and80psi.
Service applications of more than 80 psi cause the blend
back piston to begin to move. Service air pressure acting
on the full diameter of the blend back piston over comes
the resistance of reservoir pressure acting on the large
diameterofthe otherside. Above80 psi theratiobetween
control and delivered air pressure is reduced and “blends
back” from a proportioned delivery to a full 1 to 1 delivery.
Complete“blendback”toa1for 1deliveryisachievedwhen
a full brake application is made.
SERVICE BRAKES RELEASING - BOBTAIL
TRACTOR (FIGURE 8)
When the brake application is released, all air pressure
frombetweentheclosed proportioningpistoninletvalveand
theATR-2™valve’s service port returns to the brake valve
and is exhausted. Air from above the relay piston, flows
back to the proportioning piston causing it to move. As it
moves,theproportioningpistonunseats theexhaust valve
allowing air from above the relay piston to escape to
atmosphere. Reducing the air pressure above the relay
piston, causes pressure beneath it to lift the piston away
fromtheexhaust valve. Airfromtheservice brakechambers
returnsto theATR-2™valveand flowsouttheopenexhaust.
CONTROLLER
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
INLET EXHAUST
REAR AXLE
RESERVOIR
TRAILER SUPPLY
PROPORTIONING
PISTON
TRACTION
SOLENOID
INLET EXHAUST
MODULATOR
FIGURE 6 - TRACTOR - TRAILER SERVICE BRAKE RELEASING
SERVICE BRAKE

5
TRACTION CONTROL - SERVICE APPLICATION
GENERAL
While under the control of an antilock traction controller,
the ATR-2™valve’s solenoid is able to initiate a brake
applicationthatallows thetraction systemtocontrol wheel
spinuponacceleration under25 mph. Whenwheel spinis
detectedand thevehicleisstopped,ormovingatanyspeed
up to 25 mph, the antilock traction controller instantly
energizes the solenoid in the ATR-2™valve which then
appliesairto eachof the rearaxle modulatorsasshown in
Figure12. Themodulatorsareequippedwithsolenoidvalves
FIGURE 7 - BOBTAIL TRAILER SERVICE BRAKES APPLYING (LESS THAN 80 PSI)
CONTROLLER
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
INLET EXHAUST
REAR AXLE
RESERVOIR
TRAILER SUPPLY
PROPORTIONING
PISTON
TRACTION
SOLENOID
INLET EXHAUST
MODULATOR
SERVICE BRAKE
FIGURE 8 - BOBTAIL TRAILER SERVICE BRAKES HOLDING
CONTROLLER
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
INLET EXHAUST
REAR AXLE
RESERVOIR
TRAILER SUPPLY
PROPORTIONING
PISTON
TRACTION
SOLENOID
INLET EXHAUST
SERVICE BRAKE
MODULATOR

6
alsoand becausethey arealso controlledby thecontroller,
thesolenoidvalvesin theappropriatemodulatorareopened
andclosedtogentlypumpthebrakeonthe spinningwheel
only. Thisgentlebrakeapplicationforces thedifferentialto
drivethestationary orslowlyspinning wheel.
TYPICAL ANTILOCK - TRACTION SYSTEM
(PARTIAL)
Reservoirairpressure isconstantlypresent atthetraction
solenoid. Whenthe electroniccontrollerdetectswheelspin
itenergizesthe solenoidandinresponsethesolenoid opens
momentarily. While the solenoid is open, air is delivered
throughinternalpassages tothedouble checkvalve. The
check valve diaphragm flexes in response and seals the
passageto theopen exhaustofthebrakevalve. Once past
thedoublecheckvalve,airfromthesolenoidflows through
therestofthevalveinthesamemannerasanormalservice
brakeapplicationand airis deliveredoutthe deliveryports
oftheATR-2™valve.
When the electronic controller de-energizes the solenoid,
airbetweenthesolenoidandthedouble checkvalvereturns
to the solenoid and is exhausted. Air between the relay
piston and double check valve is exhausted at the brake
valve while delivery pressure is exhausted at the main
ATR-2™valve’sexhaustport.
PREVENTIVE MAINTENANCE
GENERAL
Perform the tests and inspections presented at the
prescribedintervals. If theATR-2™valvefailstofunction as
described,orleakageisexcessive,itshouldberepaired or
replacedwithanew orgenuineBendixremanufacturedunit,
availableatany authorizedpartsoutlet.
EVERY 3 MONTHS, 25,000 MILES OR 900
OPERATING HOURS
1. Remove any accumulated contaminates and visually
inspectthe exteriorforexcessive corrosionandphysical
damage.
2. Inspect all air lines connected to the ATR-2™valve for
signs of wear or physical damage. Replace as
necessary.
3. Testair linefittings forexcessive leakageand tightenor
replace as necessary.
4. Performthe LeakageTestdescribed inthismanual.
EVERY YEAR, 100,000 MILES, OR 3,600
OPERATING HOURS
1. PerformtheOperationandLeakageTestsdescribed in
this manual.
FIGURE 10 - BOBTAIL TRAILER SERVICE BRAKES RELEASING
CONTROLLER
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
INLET EXHAUST
REAR AXLE
RESERVOIR
TRAILER SUPPLY
PROPORTIONING
PISTON
TRACTION
SOLENOID
INLET EXHAUST
SERVICE BRAKE
MODULATOR
FIGURE 9 - ATR-2™VALVE PRESSURE DELIVERY CURVE
Tractor
Trailer
Combination
Service Brake Chamber Pressure
0 psi
0 psi Service Port Pressure
Bobtail
Tractor
EXHAUST

7
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
enginebe inoperation,EXTREME CAUTIONshould
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Useonly theproper tools andobserve
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems,make certain todrain theairpressurefrom
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS™
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommendedprocedures, deactivatethe electrical
system in a manner that safely removes all
electrical power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.
8. Use only genuine Bendix®replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
11. For vehicles with Antilock Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lampshould beON) priortoperforming anyvehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.
OPERATION & LEAKAGE TESTS
GENERAL
Achangein vehiclebrakingcharacteristicsor alowpressure
warningmayindicatea malfunctioninoneorthe otherbrake
circuit, and although the vehicle air brake system may
continue to function, the vehicle should not be operated
until the necessary repairs have been made and both
braking circuits, including the pneumatic and mechanical
devices are operating normally. Always check the vehicle
brake system for proper operation after performing brake
workandbeforereturningthe vehicleto service.
To properly test the function of theATR-2™valve, a pair of
test gauges or gauges of known accuracy must be used.
OPERATION TEST
1. Drainair pressurefrom allvehiclereservoirs.
FIGURE 11 - TRACTION CONTROL BRAKE APPLICATION
CONTROLLER
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
INLET EXHAUST
REAR AXLE
RESERVOIR
TRAILER SUPPLY
PROP. PISTON
TRACTION
SOLENOID
INLET EXHAUST
SERVICE BRAKE
MODULATOR

8
FIGURE 12 - PARTIAL ANTILOCK TRACTION SYSTEM SCHEMATIC
TypicalAntilock-TractionSystem(partial)
REAR AXLE
BRAKE
MODULATOR
MODULATOR
REAR AXLE
BRAKE
SPEED
SENSOR
EXCITER
BRAKE
VALVE
AT-30BP™ANTILOCK
TRACTION ASSY.
SPEED
SENSOR
EXCITER
BRAKE
CHAMBER
MODULATOR
ENGINE CONTROL
MODULE (ECM)
RETARDER
SWITCH
TRACTION
SWITCH
TRACTION DASH LAMP
ANTILOCK DASH LAMP
TRAILER ABS
(IF SO EQUIPPED)

9
2. Install a gauge at theATR-2™valve service port and at
one of the delivery ports, then install a gauge in each.
3. Connectthe tractorserviceandemergency“glad hands”
(hose couplings) to hose couplings that have been
plugged, or alternatively, to a trailer. Build the tractor
systemair pressuretogovernorcut-outand make4to 5
full brake applications. Check the air fittings at the
ATR-2™valve forleakage. Tightenasneeded.
4. Withthetrailersupplyvalve(dashcontrolw/redoctagonal
button)andsystem parkcontrol (dashcontrol w/yellow
diamond button) activated for tractor/trailer operation,
apply and release the brakes several times and check
for prompt application and release at each wheel. If
prompt reaction is noted at some, but not all wheels,
test the antilock modulator between the ATR-2™valve
and the brake chamber for proper operation. If a
“sluggish”responseis notedat allwheels, inspectfora
kinked or obstructed air line leading to or from the
ATR-2™valve. If a complete release of the brakes is
noted at some, but not all wheels, test the antilock
modulator between the ATR-2™valve and the brake
chamberfor properoperation. If anincomplete release
isnoted atall wheels,inspect fora kinkedor obstructed
airline leadingto orfrom theATR-2™valve.
5. ChecktheATR-2™valvedifferentialpressurebyapplying
10 psi to the service port and noting the pressure
registered at the delivery port. Subtract delivery port
pressure from the 10 psi service pressure to obtain the
differential. Comparethe measureddifferential withthe
pressurespecifiedfortheATR-2™valvepartnumber(see
the I.D. washer also for the differential). NOTE: For
ATR-2™valves not incorporating a relay piston return
spring(14) the measured differential should be
approximately 4 psi. When a spring is in use, the
differential willbehigher.
6. Makeandholdafull(100psiorgreater)brakeapplication
andnote thatfull pressureis deliveredtothechambers.
7. Activatethe dashmountedtrailersupplyvalve forbobtail
tractoroperation. Thenmakeaslowbrakeapplication,
increasing the pressure at the ATR-2™valve’s service
portto 20psi whilewatching thereaction atthe delivery
port gauge. Note that delivery pressure rises to
approximately 5 to 10 psi and remains constant while
service pressure continues to rise to 20 psi. Release
theapplication.
8. Makeanother brakeapplicationandslowlyincrease the
pressureattheATR-2™valve’sservice portto between
60and 70psi whileobserving thegauge installedat the
deliveryport. Notethatwhenserviceportpressure rises
to between 20 and 30 psi, delivery pressure begins to
rise above the initial pressure noted in step 6. The rise
ofdeliverypressure shouldbe ata proportionedrateof
approximately3to1. At70psiservicepressure,delivered
pressure should be 15 to 25 psi.
9. Make a full brake application and note that both test
gauges register the same pressure. IMPORTANT: If
during testing, the service port pressure is SLOWLY
increasedfrom approximately70 psito afull (100psi or
greater)brake application,theATR-2™valve MAYbegin
to cycle between an apply and exhaust mode. This
conditionisnormalwhiletheATR-2™valveistransitioning
from the proportioning mode to the full delivery mode
andwill onlyoccur ifthe serviceapplication isSLOWLY
increased as described. Cycling will not occur or can
be stopped by increasing or decreasing service port
pressure.
10. DisconnecttheATR-2™valve’stwopinsolenoidconnector
from the wire harness. Apply the probes of a volt-ohm
metertotheconnectorleadingtothesolenoidandnote
the resistance of the solenoid is between 10 and 12
ohms.
11. Applyand removevehicle power(12 vdc)tothetwopin
connector half leading to the ATR-2™valve (solenoid)
whileobserving thebrakechamber gauges. Notethata
full brake application is made and held while power is
applied to the ATR-2™valve’s solenoid and that it is
releasedwhen powerisremoved.
12. Remove thetestgauges fromtheATR-2™valve.
LEAKAGE TESTS
1. Buildthe airsystem pressuretogovernorcut-out. With
thedashmountedtrailersupplyvalveactivatedfortractor/
traileroperation,applyasoapsolutiontoallthreeexhaust
ports(two incoverand oneinbody). The leakagenoted
shouldnot exceeda 1”bubble inless than3 secondsat
any exhaust port.
2. Makeand holda fullbrake applicationandapplyasoap
solutiontoallthreeexhaustportsand aroundthe cover
where it joins the body. The leakage noted should not
exceeda1”bubbleinlessthan3secondsatanyexhaust
port.
IftheATR-2™valvefailsto functionasdescribed,orleakage
is excessive, it should be replaced with a new or genuine
Bendix remanufactured unit or repair using maintenance
kitpiecenumber 109359,availableatany Bendixauthorized
parts outlet.
VEHICLE PREPARATION
1. Parkthe vehicleonalevelsurface andblockthewheels
and/or hold the vehicle by means other than the air
brakes.
2. Drainthe airpressure fromall vehiclereservoirs.
REMOVAL
1. Identifyand markor labelall electricalwiring harnesses
and air lines and their respective connections on the
assembly to facilitate ease of installation.
2. Disconnect the air lines and wire harnesses.
3. Removethecontrollerandvalveassembly(ATR-2™valve)
fromthe vehicle.
INSTALLATION
1. Install the assembled unit on the vehicle.
2. Reconnect all air lines and wire harnesses to the unit
using the identification made during REMOVAL step 1.

10
3. After installing the unit, perform the “OPERATION &
LEAKAGE TESTS” for the air valve before placing the
vehiclein service.
DISASSEMBLY
PREPARATION FOR DISASSEMBLY
1. Removeall airfittings andplugs fromthe valve.
2. Markthe relationshipofthevalvecover(2)tothebody(1)
and,ifthevalveis equippedwithamountingbracket(41),
mark the relationship of the bracket to the cover and
body(1).
3. Mark the relationship of the electronic controller(39) to
thecover(2).
DISASSEMBLY
The following disassembly and assembly procedure is
presented for reference purposes only. Instructions
packagedwithrepair andmaintenancekits shouldalways
befollowedinstead oftheinstructions presentedhere.
CAUTION: The valve may be lightly clamped in a bench
viseduring disassembly, however, overclamping willresult
in damage to the valve and result in leakage and/or
malfunction. If a vise is to be used, position the valve so
thatthejawsbearon thesupply portson opposingsides of
thevalve body.
1. Whileholding theexhaustcover(4),removetheretaining
ring(3) that secures it to the body(1).
2. Removethe exhaustcover(4) alongwith botho-rings(5
& 6).
3. Remove the valve spring(7), valve retainer(8), and the
valveassembly(9) fromthebody(1).
4. Referring to Figure 2, remove and retain the four cap
screws(38) that secure the electronic controller(39) to
thecover(2),thenseparateandretainthecontroller(39),
fromthecover(2).
5. Remove and retain the two long cap screws(10),
washers(45and46)andnuts(43)thatsecurethecover(2)
tothebody(1).
6. Remove and retain the two cap screws and lock
washers(42)that securethebracket(41) tothecover(2),
thenremove andretain thebracket.
7. Remove and retain the two short cap screws(40) that
securethe cover(2)to thebody(1).
8. Separatethe cover(2)fromthebody(1), thenremovethe
sealingring(35) ando-ring(11).
9. Removethe relaypiston(12)and relaypistonspring(14)
from the body(1). NOTE: The relay piston spring, item
14 is not used in all valves.
10. Remove theo-ring(13)from therelaypiston(12).
11. Removetheretainingring(15). Thenremovecheckvalve
seat(16), with o-rings(20 & 21). Remove o-rings(20 &
21)fromthecheckvalveseat.
12. Removethecheckvalve(17),guide(18),andspring(19).
13. Remove the inlet seat(36) with o-rings(37 & 44), then
remove and discard o-rings(37 & 44) from the inlet
seat(36).
14. Removethespring(22)thenremoveandretainthespring
cage(23)fromthe valvecover(2).
15. Use shop air at the control port to extract the blend
back piston(24) from the valve cover(2). Retain the
piston(24)butremove anddiscardbotho-rings(25&26).
16. Remove theentire,assembled proportioningpiston(28)
from the valve cover(2). Then remove and discard
o-rings(27& 29).
17. Remove retainingring(30). Remove inletseat(32) then
remove and discard inlet valve(33) and spring(34).
Removeand discardo-ring(31) fromtheinletseat(32).
CLEANING & INSPECTION
1. Usingmineral spiritsoranequivalentsolvent, cleanand
thoroughly dry all metal parts. Do not damage bores
with metal tools.
2. Washall retained,non-metalliccomponents (KeyNos.
12,23,24) inasoap andwater solution makingcertain
torinseand drythoroughly.
3. Inspect the interior and exterior of all metal parts that
will be reused for severe corrosion, pitting and cracks.
Superficialcorrosionand/or pittingontheexteriorportion
ofthebody(1)andcover(2) isacceptable. Replace the
entire valve if the interior of the body or cover exhibit
signs of corrosion or pitting.
4. Inspect each non-metallic component for cracks, wear
ordistortion. Replacetheentirevalveifthese conditions
arefound.
5. Inspect the bores of both the body(1) and cover(2) for
deepscuffingorgouges. Replacetheentirevalveifeither
arefound.
6. Make certain the air channel running between the top
surface of the body(1) and its supply port is clear and
freeof obstruction.
7. Make certain all air channels and exhaust passages in
thevalvecover(2)areclearandfreeofobstruction. Make
sure the .060" hole in the control port is open.
8. Inspectthepipethreadsinthebody(1)andvalvecover(2).
Makecertainthey areclean andfreeof threadsealant.
9. Inspectthe relaypistonspring(14) forsignsof corrosion,
pitting and cracks. Replace as necessary.
10. Inspect all air line fittings for corrosion and replace as
necessary. Makecertaintoremoveallold threadsealant
beforereuse.
ASSEMBLY
1. Priortoassembly,lubricateallo-rings,seals,andpistons,
aswellasbodyandcoverbores,usingsiliconelubricant.
2. Installo-ring(31) onthe newinletvalveseat(32).
3. Install the small end of the new inlet/exhaust valve
spring(34)overtherubberofthenewvalve(33)making
sure the spring coils rest on the valve’s four tabs.
4. Insertthespringandvalveintothevalveseat(32),making
sure the four tabs are within the seat’s bore.
5. Insert the valve, seat and spring assembly into the
proportioningpiston(28)andwhileholdingtheseat(32)

11
FIGURE 13 - AntiLock TractionAssembly Exploded View
1
2
3
4
56
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30 31 32
33 34
35 36
37
38
40
41
42
43
44
*Itemincludedinmaintenancekitpiecenumber 109359
45
Key Description Qty.
1 Body 1
2 Cover 2
3* RetainingRing 1
4* Exhaust Cover 1
5* O-Ring 1
6* O-Ring 1
7* ValveSpring 1
8* ValveRetainer 1
9* Inlet/ExhaustValve 1
10 LongCapScrew 2
11* O-Ring 1
12 RelayPiston 1
13* O-Ring 1
14 RelayPistonSpring(ifused) 1
15* RetainingRing 1
16 CheckValveSeat 1
17* Check Valve 1
18 ValveGuide 1
19* Spring 1
20* O-Ring 1
21* O-Ring 1
22* Spring 1
23 Cage 1
Key Description Qty.
24 ProportioningPiston 1
25* O-Ring 1
26* O-Ring 1
27* O-Ring 1
28 BlendBackPiston 1
29* O-Ring 1
30* RetainingRing 1
31* O-Ring 1
32 ValveSeat 1
33* Valve 1
34* Spring 1
35* SealingRing 1
36 InletSeat 1
37* O-Ring 1
38 Cap Screw 4
39 Controller 1
40 Short Cap Screw 2
41 Bracket 1
42 Cap Screw 2
43 Nut 2
44* O-Ring 1
45 Washer 2
46 Washer 2
46
39

12
in place, install retaining ring(30) to secure it in the
piston(28). Makecertaintheretainingringisfully seated
in its groove. Make sure the valve is straight, against
the exhaust seat and free to move.
6. Install both the large and small diameter o-rings(27 &
29)on theproportioning piston(28).
7. Install both the large and small diameter o-rings(25 &
26) on the blend back piston(24), then insert the small
diameter of the proportioning piston(28) into the small
diameterendoftheblend backpiston(24).
8. Carefullyinserttheassembledproportioningandblend
back pistons(24 & 28) into the bore in the cover(2). Do
not cut or pinch the o-rings.
9. With the bore of the cover facing up, install the spring
cage(23) in the blend back piston(24) so that its flat
side rests against the blend back piston. The concave
sideofthe springcageshouldface towardthespring(22)
which is installed next.
10. Install thespring(22) inthecage(23)sothatitscoilsare
within the I.D. of the cage.
11. Installthe smalland largediameter o-rings(44& 37)on
the inlet seat(36) then insert the inlet seat into the bore
inthe cover(2).
12. Install thesmall andlarge diametero-rings(21 &20) on
thecheck valveseat(16).
13. Install the spring(19) on the inlet seat(36) so that the
small diameter fits over and around the air passage
through the center of the inlet seat.
14. Install the check valve(17) and valve guide(18) in the
check valve seat(16). Note; The check valve must be
installed so that the “top hat” portion fits into the valve
seat(16). Install the valve guide(18) so that its flange
contains (surrounds) the coils of the large end of the
spring(19), when the valve seat(16) is installed in the
cover(2). Useasmallamount greasetoholdthese parts
inthe valveseat(16).
15. Installtheassembledvalve seat(16)withthecheckvalve
andvalveguide(17&18)intothecover(2)boreandwhile
holding it in place install the retaining ring(15). Make
certain the retaining ring is fully seated in its groove.
16. Install the valve retainer(8) on the inlet and exhaust
valve(9) so that the flange of the retainer(8) surrounds
therubberportionofthevalve. Installtheinletandexhaust
valvein thebody(1).
17. Install theinletandexhaustvalve returnspring(7) inthe
body(1).
18. Install thelarge andsmalldiametero-rings(5& 6)in the
exhaust cover(4), then install the exhaust cover in the
body(1)taking carenottodamagethe o-rings. Holdthe
exhaustcoverinplace.
19. While depressing the exhaust cover(4), install the
retaining ring(3) in the body(1). Make certain the
retainer(3) is fully seated in its groove in the body.
20. If the valve was equipped with a relay piston return
spring(14),install thespring inthe body, largediameter
first.
21. Using lubricant to hold them in place, install the large
andsmallsealingrings(11 &35) onthe cover(2).
22. Install theo-ring(13)ontherelaypiston(12),theninstall
the piston in the body(1).
23. Note therelationship marksmadepriortodisassembly,
then install the cover(2) on the body(1). Secure the
cover(2) on the body(1) using the two, short cap
screws(40). Again,notingtherelationshipmarks, secure
the bracket(41) on the cover(2) and body(1) and using
the two long cap screws(10), washers(45 and 46) and
twonutsandwashers(43). Torquethefour capscrews
to 120 to 150 lb. in.
24. Installthetwocapscrews(42)thatsecurethebracket(41)
tothecover(2) andtorque to180 -220 poundinches.
25. Notingtherelationshipmarksmade duringdisassembly,
secure the controller(39) to the cover(2) using the four
cap screws(38). Torque the four cap screws to 50-80
poundinches.
26. Install allairline fittingsandplugs makingcertainthread
sealingmaterial doesnot enterthe valve.
27. Install the rebuilt valve on the vehicle and perform the
OPERATIONANDLEAKAGETESTSbeforeplacingthe
vehiclein service.
O-RingIdentification
Key Description Qty. I.D. O.D. W
5 O-Ring 1 0.862 1.068 0.103
6 O-Ring 1 1.424 1.63 0.103
11 O-Ring 1 3.487 3.693 0.103
13 O-Ring 1 3.234 3.512 0.139
20 O-Ring 1 1.362 1.568 0.103
21 O-Ring 1 1.114 1.254 0.07
25 O-Ring 1 1.112 1.318 0.103
26 O-Ring 1 0.737 0.943 0.103
27 O-Ring 1 0.412 0.552 0.07
29 O-Ring 1 0.739 0.879 0.07
31 O-Ring 1 0.489 0.629 0.07
37 O-Ring 1 1.356 1.496 0.07
44 O-Ring 1 1.176 1.316 0.07
SECTIONAL SIDE
VIEW OF HOW AN
O-RING IS
MEASURED.
1234
1234
1234
1234
1234
1234
12345
12345
12345
12345
12345
I.D.”
W
O.D.”
FIGURE 14 - O-RING IDENTIFICATION CHART
O-ringsavailablein maintenancekit piece no.109359.
BW1791 © 2004 Bendix Commercial Vehicle Systems LLC All rights reserved. 6/2004 Printed in U.S.A.