Introduction
This manual is designed to provide information for you to understand, use, maintain, and
service your trailer running gear system. Your axles are manufactured by Dexter. Since
1960, Dexter’s experience in the design, testing, and manufacturing of trailer axles has
resulted in the most complete product line in the industry. The Dexter running gear system
consists of axles, suspensions, and braking systems which are engineered to provide you
the finest towing and stopping performance available today.
Two Dexter philosophies are at work to provide you the best product available and have
enabled us to maintain our position of leadership. First, we operate on the theory that
“there is always a better way” for a product to operate, to be manufactured, and/or to be
serviced. We are constantly striving to find that better way.
Secondly, we maintain the highest quality control standards in the industry and adhere
to ISO 9001:2015. Dexter has operated with detailed documented processes and
procedures long before completing ISO Certification, continually placing quality and
customer service as the focus. This ensures that critical components including axle
beams, hubs, drums, spindles, and braking systems are manufactured to the highest
quality standards so that we can provide our customers with dependable products, the
most comprehensive product offering and reliable, consistent customer service.
Trusting is hard. Knowing who to trust even harder. Through vertical integration we engineer,
design, manufacture and test virtually every part in-house to ensure superior quality trailer
running gear. We fuss over details, so you don’t have to. Trust Dexter.
Visit us online at www.dexteraxle.com.

Introduction

Important Safety Notice.......................................................................................................4
Getting Started - Setup and Adjustment...............................................................................4

Braking Systems - Electric

Electric Brakes.....................................................................................................................5
Features..............................................................................................................................6
Parking Brake Option..................................................................................................6
Self Adjusting Feature................................................................................................6
Brake Controllers........................................................................................................7
Typical Trailer Wiring..................................................................................................10
How to Use Your Electric Brakes Properly..................................................................11
Trailer Wire Size Chart...............................................................................................11
Synchronizing Your Trailer Brakes..............................................................................12
General Maintenance Electric Brakes.................................................................................13
Brake Adjustment.....................................................................................................13
Brake Cleaning and Inspection.................................................................................14
Brake Lubrication.....................................................................................................14
Magnets............................................................................................................................15
Shoes and Linings.............................................................................................................16
Introduction to Troubleshooting..........................................................................................17
Troubleshooting.................................................................................................................17
Troubleshooting Chart - Electric................................................................................18
How to Measure Voltage...........................................................................................20
How to Measure Amperage.......................................................................................20
Magnet Amperes Chart.............................................................................................21

Table of Contents

Braking Systems - Hydraulic

Hydraulic Brakes...............................................................................................................23
Hydraulic Drum Brake Operation........................................................................................24
Duo-Servo................................................................................................................24
Uni-Servo.................................................................................................................24
Self-Adjusting Mechanism for 12 1/4" Brakes.........................................................25
Hydraulic Parking Brake Option................................................................................25
Hydraulic Disc Brakes..............................................................................................27
Actuation Systems.............................................................................................................28
Electrical Schematic.................................................................................................28
Troubleshooting Guide..............................................................................................29
General Maintenance - Hydraulic Brakes...........................................................................31
Drum Brake Adjustment - Manual.............................................................................31
Wheel Cylinders.......................................................................................................32
Brake Lines..............................................................................................................32
Shoes and Linings....................................................................................................32
Hardware.................................................................................................................33
Instructions for Brake Caliper Kit - 3.5K Disc Brakes.................................................33
Instructions for Brake Rotor Kit - 3.5K Disc Brakes...................................................34
Instructions for Brake Rotor Kit - 6K or 8K Disc Brakes.............................................36
Instructions for Brake Hub/Rotor Kit - 7K Disc Brakes..............................................37
Instructions for Brake Pad Kit - 6K, 7K or 8K Disc Brakes.........................................39
Instructions for Brake Caliper Kit - 6K, 7K or 8K Disc Brakes....................................42
Introduction to Troubleshooting..........................................................................................45
Troubleshooting Chart - Hydraulic.............................................................................46

Hubs/Drums/Bearings

Hubs/Drums/Bearings.............................................................................................48
Hub Removal - Standard Bearings............................................................................49
Brake Drum Inspection.............................................................................................49
Bearing Inspection...................................................................................................50
Bearing Lubrication - Grease...................................................................................52

Axle Installation

Axle & Suspension Installation..........................................................................................64

Suspensions

Suspension Systems.........................................................................................................65
Double Eye Leaf Springs...........................................................................................65
Grease Lubricated Suspension Bushings..................................................................66
Slipper Leaf Springs.................................................................................................66
Inspection and Replacement....................................................................................67
Suspension Fastener Torque Values..........................................................................67
Torflex® Suspension..................................................................................................69
Airflex® Suspension..................................................................................................70

Wheels and Tires

Wheels..............................................................................................................................72
Wheel Selection.......................................................................................................72
Torque Requirements................................................................................................73
Wheel Torque Requirements.....................................................................................74
Maximum Wheel Fastener Torque..............................................................................75
Tires..................................................................................................................................76
Tire Wear Diagnostic Chart........................................................................................77

Replacement Parts/Kits

Magnet Replacement Kits and Brake Nut Torque.......................................................78
Seal Replacement Reference...................................................................................78
Brake Shoe Replacement Kits..................................................................................79
Bearing Replacement Chart......................................................................................80

Storage

Storage Preparation...........................................................................................................81
After Prolonged Storage - Inspection Procedures................................................................82
Trip Preparation Checklist..................................................................................................83

Maintenance Schedule

Maintenance Schedule Chart.............................................................................................84

Warranty

Limited Warranty................................................................................................................85

Axle Identification

Axle Identification..............................................................................................................88

Video Gallery

Dexter Video Gallery..........................................................................................................90

Table of Contents

Bearing Lubrication - Oil...........................................................................................52
Recommended Wheel Bearing Lubrication Specifications.........................................53
Seal Inspection and Replacement............................................................................55
Bearing Adjustment and Hub Replacement...............................................................56
Typical E-Z Lube® After Spring 2002..........................................................................57
E-Z Lube® Lubrication...............................................................................................57
Nev-R-Lube® Drums/Bearings............................................................................................59
Drum Removal.........................................................................................................60
Bearing Inspection...................................................................................................60
Nev-R-Lube® Bearing End Play Inspection.................................................................61
Bearing Replacement and Drum Installation.............................................................62

Important Safety Notice
Appropriate service methods and repair procedures are essential for the safe,
reliable operation of all running gear as well as the personal safety of the
individual doing the work. This manual provides general directions for performing
service and repair work with tested, effective techniques. Following these
guidelines will help assure reliability.
There are numerous variations in procedures, techniques, tools, parts for
servicing axles, as well as in the skill of the individual doing the work. This
manual cannot possibly anticipate all such variations and provide advice or
cautions as to each. Anyone who departs from the instructions provided in this
manual must first establish that they neither compromise their personal safety
nor the vehicle integrity by their choice of methods, tools, or parts.
Refer to your vehicle manufacturer’s owners manual for additional procedures,
techniques, and warnings prior to performing any maintenance or repairs.

!

CAUTION

This is the safety alert symbol. It is used to alert you to potential
injury hazards. Obey all safety messages that follow this symbol to
avoid possible injury or death.

Getting Started - Setup and Adjustment

Introduction

For proper performance, all new axles should have the following checked at the
specified intervals:
•

Wheel Nut Torque: at 10, 25, and 50 miles

•

Brake Adjustment: at 200 and 3,000 miles

•

Tire pressure: to manufacturer’s requirements

•

Brake synchronization: set brake controller per controller manufacturer’s
directions

-4-

The electric brakes on your trailer are similar to the drum brakes on your
automobile. The basic difference is that your automotive brakes are actuated
by hydraulic pressure while your electric trailer brakes are actuated by an
electromagnet. With all of the brake components connected into the system, the
brake will operate as follows:
Retractor Spring

Primary Shoe

Secondary Shoe

Actuating Lever

Shoe Hold
Down Spring

Front of Brake
Magnet

Adjuster
Adjuster Spring

When the electrical current is fed into the system by the controller, it flows
through the electromagnets in the brakes. The high capacity electromagnets are
energized and are attracted to the rotating armature surface of the drums which
moves the actuating levers in the direction that the drums are turning.
The resulting force causes the actuating cam block at the shoe end of the lever
to push the primary shoe out against the inside surface of the brake drum. The
force generated by the primary shoe acting through the adjuster moves the
secondary shoe out into contact with the brake drum.
Increasing the current flow to the electromagnet causes the magnet to grip
the armature surface of the brake drum more firmly. This results in increasing
the pressure against the shoes and brake drums until the desired stop is
accomplished.

-5-

Braking Systems - Electric

Electric Brakes

Features
Electrically actuated brakes have several advantages over other brake actuation
systems.
1. They can be manually adjusted at the controller to provide the correct
braking capability for varying road and load conditions.
2. They can be modulated to provide more or less braking force, thus
easing the brake load on the towing vehicle.
3. They have very little lag time from the moment the tow vehicle’s brakes
are actuated until the trailer brakes are actuated.
4. In an emergency situation, they can provide some braking independent
of the tow vehicle.

Parking Brake Option
(Not available on all sizes)

Braking Systems - Electric

Dexter electric brakes with parking brake option are mechanically operated by
a cable. Cable force applied to the parking lever creates a torque through the
pivot pin and cam assembly. Torque transferred to the parking cam results in a
spreading force between the primary and secondary shoes. The shoes, in turn,
move towards the drum until contact is made. Friction generated between the
drum and lining contact surface keeps the drum from rotating under normal
loading conditions.

Self Adjusting Feature
(Not available on all sizes)
Dexter electric brakes may be equipped with a forward self-adjust feature.
This will allow the brakes to adjust on both forward and reverse stops. Brake
adjustment occurs when lining wear results in enough gap between the shoes
and the brake drum surface. This added clearance will allow the adjuster
mechanism to rotate the screw assembly at the bottom of the brake. That action
expands the distance between the shoes and thus closes the gap to the drum
surface.

-6-

Electric brake controllers provide power to the magnets to actuate the trailer
brakes. Dexter offers a state-of-the-art inertial controller called the Predator
DX2®. This controller features a patented accelerometer design which senses
the deceleration of the towing vehicle and sends a proportional voltage to the
electric trailer brakes. Other features include a visual gain setting for quick and
easy adjustment and a digital LED display to show the voltage output. A manual
override sends full voltage to the trailer brakes, regardless of gain setting,
for emergency conditions and also illuminates the brake lights to warn of an
impending stop.
Most electric brake controllers provide a modulation function that varies the
current to the electric brakes with the pressure on the brake pedal or amount of
deceleration of the tow vehicle. Electronic or timing controllers do not provide
proportional modulation. These controllers tend to be inexpensive but not the
best choice for optimum braking. It is important that your brake controller
provide approximately 2 volts to the braking system when the brake pedal is
first depressed and gradually increases the voltage to 12 volts as brake pedal
pressure is increased. If the controller “jumps” immediately to a high voltage
output, even during a gradual stop, then the electric brakes will always be fully
energized and will result in harsh brakes and potential wheel lockup.

-7-

Braking Systems - Electric

Brake Controllers

Braking Systems - Electric

Dexter Electric Brakes
Wired in parallel.

Breakaway Battery
Provides power to actuate
trailer brakes in the event of
trailer breakaway.
Breakaway Switch
Switches battery power
to brakes if
breakaway occurs.

-8-

Battery
Connect controller directly.

Connector
Used to connect and disconnect
trailer and tow vehicle.
(Always ground trailer brakes
through connector).

-9-

Braking Systems - Electric

Controller
Electric brake controller
provides power to the
magnets to actuate the
trailer brakes.

Typical Trailer Wiring
Double
Filament
Bulb
Green
License Tail &
Running Lights
Terminal #3

Red

Stop & Left Turn Signal
To Terminal #5

Yellow

Auxiliary Circuit
Terminal #7
Grey

White

#1 Common Ground
#3 To Tail Running &
License Lights
#5 Stop & Left Turn

Green

Auxiliary Circuit
Terminal #8

Red
Black

Battery Charge
Terminal #4 Black

#4 Battery Charge

Yellow #7 Aux. Circuit
Orange #9 Aux. Circuit
#6 Stop & Right Turn
#2 Electric Brake
#8 Aux. Circuit

Brown
Electric Brake
Terminal #2 Blue

Breakaway Switch

Batt.

Common Ground
Terminal #1

White
Brown

Electric Brake
Ground Terminal
#1 White
Double
Filament
Bulb

Blue
Grey

Orange

Auxiliary Circuit
Terminal #9
Stop & Right Turn Signal
Terminal #6

Trailer

Towing Vehicle

9-Circuit Receptacle

3

N

RED

BROWN

BL

U

E

Brakes
2

Brakes

2

GR

EY

8

N
OW
BR
6

Auxiliary

Auxiliary

3

Clearance &
Tail Lights

4

Battery
Charge

7

E

Braking Systems - Electric

Stop &
RH Turn

Stop &
LH Turn

D

YELLOW

BLU

E

IT

H

W
1

Ground

6

1

5

RE

N

7

E
ANG
OR

EE

5

9

Ground

K

YELLOW

Auxiliary

GR

AC

Stop &
LH Turn

4