www.dexteraxle.com
2900 Industrial Parkway East n Elkhart, IN 46516
Phone: 574-295-7888 n Fax: 574-295-8666

ISO 9001:2015 Certified

05/17

© 1990 - 2017 Dexter Axle Company. LIT-006-00

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

Maintenance Schedule...................................................................................4
Important Safety Notice..................................................................................5
Getting Started - Setup and Adjustment........................................................5
Answers to Commonly Asked Questions.......................................................6

Braking Systems - Electric

Electric Brakes...............................................................................................8
Features.......................................................................................................10
Self Adjusting Feature..........................................................................11
Brake Controllers..................................................................................11
How To Use Your Electric Brakes Properly...........................................12
Trailer Wire Size Chart.........................................................................12
Synchronizing Your Trailer Brakes........................................................13
General Maintenance - Electric Brakes........................................................14
Brake Adjustment.................................................................................14
Brake Cleaning and Inspection............................................................15
Brake Lubrication.................................................................................15
Magnets........................................................................................................16
Shoes and Linings........................................................................................17
Introduction to Troubleshooting.....................................................................18
Troubleshooting............................................................................................18
Troubleshooting Chart - Electric...........................................................19
How to Measure Voltage......................................................................21
How to Measure Amperage..................................................................21
Magnet Amperes Chart........................................................................22

Table of Contents

Braking Systems - Hydraulic

Hydraulic Brakes..........................................................................................24
Hydraulic Drum Brake Operation..................................................................25
Duo-Servo............................................................................................25
Uni-Servo.............................................................................................26
Self-Adjusting Mechanism for 12¹⁄₄" Brakes.........................................26
Hydraulic Parking Brake Option...........................................................26
Hydraulic Disc Brakes..........................................................................28
Electric/Hydraulic Actuation Systems...................................................29
Vacuum/Hydraulic................................................................................29
Air/Hydraulic.........................................................................................30
Introduction to Troubleshooting.....................................................................31
Troubleshooting Chart - Hydraulic........................................................32
Electric/Hydraulic Troubleshooting Guide.............................................34
General Maintenance - Hydraulic Brakes.....................................................36
Drum Brake Adjustment.......................................................................36
Wheel Cylinders...................................................................................37
Brake Lines..........................................................................................37
Shoes and Linings................................................................................37
Hardware..............................................................................................38
Instructions for 10-12K Hydraulic Disc Brakes.....................................38
Hydraulic Disc Brake Parts...........................................................................41

Braking Systems - Air

S-Cam Air Brakes.........................................................................................42
Operation..............................................................................................42
Air Brake Components.................................................................................43
Air Chambers.......................................................................................43
Spring Brake.........................................................................................43
Slack Adjusters.....................................................................................44
S-Cams................................................................................................44
Brake Shoes.........................................................................................45
General Maintenance/Adjustment................................................................46
Brake Component Lubrication..............................................................46
12¹⁄₄" Quick Change Brakes - PQ.................................................................47
Recommended Disassembly................................................................47

Hubs/Drums/Bearings

Hubs/Drums/Bearings..................................................................................55
Hub Removal........................................................................................55
Brake Drum Inspection.........................................................................55
Bearing Inspection...............................................................................56
Bearing Lubrication - Grease...............................................................57
Bearing Lubrication - Oil.......................................................................58
Recommended Wheel Bearing Lubrication Specs...............................59
Seal Inspection and Replacement........................................................61
Installation/Adjustment.........................................................................62

Axle Installation

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

Suspensions

Suspension Systems....................................................................................65
Slipper Leaf Springs.............................................................................65
Inspection and Replacement................................................................66
Suspension Replacement....................................................................68
Torflex® Suspension..............................................................................68
Heavy Duty Suspension Axle Alignment......................................................70
Alignment/Procedure............................................................................70
Measuring............................................................................................71
Adjusting/Precautions...........................................................................72
Additional Suspension Maintenance Check.........................................72
Heavy Duty Suspension Torque Requirements....................................73
Minimum Torque Values for Bolts With Clean Dry Threads..................73

Wheels and Tires

Wheels.........................................................................................................74
Wheel Selection...................................................................................74
Torque Requirements...........................................................................75
Wheel Torque Sequence......................................................................76
Tires.............................................................................................................77
Tire Wear Diagnostic Chart..................................................................78

Replacement Parts/Kits

Fastener Torque Specifications....................................................................79
Bearing Replacement Chart.........................................................................80
Seal Replacement Reference.......................................................................80
Electric Brake Magnets................................................................................80
Brake Shoe Replacement Kits......................................................................81
Air Brake Shoe & Linings..............................................................................81
Air Brake Repair Kits....................................................................................81
Disc Brake Pad Kit........................................................................................81
Disc Brake Caliper Repair Kit.......................................................................81

Storage

Storage Preparation.....................................................................................82
After Prolonged Storage - Inspection Procedure..........................................83
Trip Preparation Checklist.............................................................................84

Warranty

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

Axle Identification

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

Video Gallery

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

Table of Contents

Recommended Reassembly................................................................47
Air Brake Automatic Slack Adjustment.................................................49
Air Brake Manual Slack Adjustment.....................................................50
Introduction to Troubleshooting.....................................................................52
Troubleshooting Chart - Air..................................................................53

Introduction

Maintenance Schedule
Item

Function Required

Weekly

Brakes

Test that they are
operational.

Brake
Adjustment

Adjust to proper operating
clearance (not required with
Nev-R-Adj® brakes).

Brake Magnets

Inspect for wear and current
draw.

Brake Linings

Inspect for wear or
contamination.

Brake Controller

Check for correct amperage
and modulation.

Brake Cylinders

Check for leaks, sticking.

Brake Lines

Inspect for cracks, leaks,
kinks.

Camshaft
Bushings

Check for wear and
breakage.

Anchor Pins
and Rollers

Lubricate with approved
grease.

Slack Adjuster
Lubrication

Lubricate with approved
grease.

Trailer Brake
Wiring

Inspect wiring for bare
spots, fray, etc.

Breakaway
System

Check battery charge and
switch operation.

Hub/Drum

Inspect for abnormal wear
or scoring.

Wheel Bearing
and Cups

Inspect for corrosion or
wear. Clean and repack.

Seals

Inspect for leakage.
Replace if removed.

Springs

Inspect for wear, loss of
arch.

Suspension
Parts

Inspect for bending, loose
fasteners and wear.

Extreme Duty
Bushings

Grease.

Hangers

Inspect welds.

Wheel Nuts
and Bolts

Tighten to specified torque
values.

Wheels

Inspect for cracks, dents, or
distortion.

Tire Inflation
Pressure

Inflate tires to mfg’s.
specifications.

Tire Condition

Inspect for cuts, wear,
bulging, etc.

3 Months or
3,000 Miles

6 Months or
6,000 Miles

12 Months or
12,000 Miles

At Every Use

•
•
•
•
•
•
•
•
•
•
At Every Use

•
•
•
•
•
•
•
•
•
•
•
-4-

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
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

-5-

Introduction

Important Safety Notice

Answers to Commonly Asked Questions
Q: Why do my brakes and hubs get so hot?
A: Braking systems use friction to slow the vehicle and the
energy used to retard the trailer is converted to heat.
Dexter brakes are designed to operate up to extremely high
temperatures during hard braking application. This heat
is noticeable on the hub and drums and is to be normally
expected on a properly functioning brake. If a brake is
malfunctioning and running excessively hot, this can be
noticed by smoking brakes or the paint burning off of the
brake drum. If this occurs, refer to the brake troubleshooting
diagram for your type of brake.
Q: Why do I have to adjust my brakes?
A: Brakes must be adjusted to compensate for the lining and
drum wear that occurs during use of the braking system.
Some brakes require manual adjustment to move the linings
closer to the drum. Refer to the brake adjustment section for
your style of brakes. Other brakes may have an automatic
brake adjuster such as the automatic slack adjusters for air
brakes.
Note: Prior to 10/96 electric and hydraulic self-adjusting
brakes adjust only during hard, reverse stops. If your driving
does not include these types of stops, you will have to
manually adjust your brakes. Designs after 10/96 adjust both
in forward and in reverse. Adjustment in reverse still requires
hard stops, while adjustment in forward motion will occur
through normal driving.

Introduction

Q: My brake linings are cracked, do I have to replace them?
A: Usually, light cracking of the surface of a brake lining
can be expected under normal use. This is not cause for
replacement. However, if the lining is missing chunks, your
brake linings or shoes will require replacement.
Q: Why do I have to torque the wheel nuts on my trailer and do
not have to do so in my car?

-6-

Q: Why can’t I lock and slide my electric brakes?
A: On an unloaded trailer, you may be able to lock up your
brakes if your electric brake controller is supplying full
amperage to the brakes. When loaded to capacity, you
may not be able to lock your brakes as electric brakes are
designed to slow the trailer at a controlled rate, and not
designed to lock up the wheels on a fully loaded trailer. Our
brakes are designed to meet all applicable safety standards.
All of our brakes will perform better after numerous burnish
stops to seat the brake linings to the drums.
Q: I don’t feel I have enough brakes or capacity on my axles.
Can I easily upgrade?
A: Usually depending on the trailer configuration, you can
upgrade your running gear to a higher capacity rating. We
recommend consulting with the trailer manufacturer first
before doing so.
Q: Can I change my brakes from electric to hydraulic or vice
versa?
A: This can be done on most axle models. We recommend
contacting the trailer manufacturer prior to changing your
braking system to identify any potential problems.

-7-

Introduction

A: The main reason is wheel capacity. Your entire car may
weigh 3,000 lbs. which is spread over four wheels, while
a 6,000 lb. trailer axle has 3,000 lbs. on a single tire
and wheel. This places greater stress on the wheel/tire
combination. The second reason is loading. Your car
is designed to have the wheels track the arc of a turn,
reducing side load on the tire and wheel. Trailers are
subjected to harsh side loads, especially in double and triple
axle configurations. These side loads work to flex the wheel
which may cause the wheel to lose torque over time. Please
follow the wheel usage instructions located later in this
manual.

Electric Brakes
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 should
operate as follows (see electric brake assembly illustration):
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.

Brake Controller

Breakaway Switch

Braking Systems - Electric

Stoplight Wire

Battery
Power Wire

Brake Wire
Ground Wire

-8-

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.

12V Battery for
Breakaway Switch

Towing Vehicle
Trailer Connection

-9-

Braking Systems - Electric

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 link then moves the secondary
shoe out into contact with the brake drum.

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.
Retractor Spring
Secondary Shoe

Primary Shoe

Braking Systems - Electric

Self-Adjusting
Cable
Actuating