INSTALLATION INSTRUCTIONS

DX6.6 (Formerly Model 660E) Brake Actuator
#
1

1A

TDE Part #
70519K

70519KD

DX Part #

Description

K68-525-20

Disc Brake Master Cylinder
Kit: master cylinder and cap, 4
mounting screws with washers, 2
rollers with matching nuts and bolts

K68-525-00

Drum Brake Master Cylinder
Kit: master cylinder and cap, 4
mounting screws with washers, 2
rollers with matching nuts and bolts

NS

11286-BLK

054-240-00

Disc Brake Solenoid - used with
Disc Brake Actuators (not shown)

2

70411

068-562-00

Latch Kit Assembly, with Drop-NGo™ Coupler, (for serial numbers
17926 and below)

2

70412

068-563-00

Latch Kit Assembly, with Drop-NGo™ Coupler, (for serial numbers
17927 and above)

3

50317

068-738-10

Emergency Stop Cable (E-stop/
Breakaway)

4

50301

074-477-00

Safety Cable with stainless steel
pin - Includes mounting screw-

5

70462K

K68-524-00

Actuator Covers, includes front
and rear cover plates and 4
mounting screws

6

48986A

068-572-00

Master Cylinder Fill Cap with
internal bladder, 2.25” Opening
(E-Models)

7

48845

074-472-00

Safety Spring with two mounting
screws

1&6
5
1
7

5

4

1A
1

1
2

IMPORTANT: READ AND UNDERSTAND THE ENTIRE
INSTRUCTION/ASSEMBLY PROCEDURE BEFORE INSTALLATION.

Read your vehicle’s owner manual on towing capacity and other towing
recommendations before installing brakes or this actuator. The DX6.6
Actuator is completely assembled and ready to bolt into place, if not
already installed. Manufactured for tongue sizes: 3”x 3”, 3”x 4” & 3”x 5”.

The DX6.6 works by the “surge” or “push” of the trailer toward the tow
vehicle. This automatically synchronizes the trailer brakes with the tow
vehicle axle brakes. When the trailer pushes against the tow vehicle, the
actuator telescopes together and applies the force to the master cylinder,
supplying hydraulic pressure to the brakes. The built in dampening shock
absorber retards the telescoping shock against the hitch ball.

!

CAUTION

Brake laws sometimes are minimum standards and you may
wish to add additional brakes to your trailer. Read your tow
vehicles owner’s manual on towing capacity and other towing
recommendations before installing brakes or this actuator.

©2019 Dexter Axle Company | www.dexteraxle.com

3

5

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1.

Bolt the actuator to the tongue using 1/2” diameter, 4” long grade
5 bolts. Lightweight tongues, less than 11 gauge, require spacer
tubes inside the tongue for reinforcement. Attachment strength
should equal or exceed 1-1/2 times trailer G.V.W.R.

2.

Hydraulic brake lines should be installed on the trailer as described
in the installation manual supplied with the brakes. Note: Some disc
brakes require the use of flexible brake lines at the connection point
on the brake caliper. Follow brake manufacturer instructions.

3.

Use a pressure type brake bleeder to bleed brakes following
manufacturer’s directions or manually bleed the brakes
following instructions on page 3. Check with your state motor
vehicle department for laws concerning minimum trailer brake
requirements. Some states may require brakes on all axles.
059-Z01-22 2019.10 | 08162-2/08057-2

!

CAUTION

!

• DO NOT REUSE BRAKE FLUID. Always use fresh DOT 3 fluid
from a fresh container. Failure to maintain proper levels of
fluid in the reservoir will cause brake failure.
• Dexter actuators and brakes are designed to use DOT 3 (or
4) brake fluid. Do not use of DOT 5 brake fluid. Use of DOT 5
brake fluid will cause damage to internal parts that can result
in loss of brake power.
4.

•

•

Road test trailer a short distance to activate the actuator several
times. Check fluid level again. Remember, low brake fluid levels will
result in hitch ball knocking.

!

•

CAUTION

AVOID sharp turns, which can cause the actuator to bind or
jackknife against the tow vehicle or cause a bend in the tongue.
Either can damage the actuator causing brake failure. AVOID
towing trailer across large bumps or dips that may over stress
the connection between the trailer and tow vehicle, as this could
result in damage to the actuator.
5.

When testing is completed, make sure master cylinder is filled to
3/8” below the top of the reservoir and filler cap is securely in
place. Road test again to make sure brakes work properly.

RATED CAPACITY: Maximum Actuator Capacity: 6600 lbs. Gross
Load, 660 lbs. Maximum Tongue Load
The actual in-service rating is limited to that of the ball and hitch being
used or the trailer manufacturer’s G.V.W.R. shown on the certification
label, whichever is lower (Note: G.V.W.R. is the Gross Vehicle Weight Rating
which includes the trailer and the load weight as a Total Gross Weight).

!

Connect safety cables or chains using crossed pattern under
tongue, or follow trailer manufacturer’s directions.

4.

Connect actuator breakaway cable S-hook to the tow vehicle only.
Do not connect S-hook to the safety cables or chains.

5.

The breakaway system is designed to only operate after the trailer
detaches from the tow vehicle and the safety chains have failed.
The breakaway is not a parking brake. Do not use as such.

6.

If the breakaway is accidentally applied, insert a flat bladed
screwdriver into the spring clip on the side of the actuator and pry
sideways pressure to release.

!

CAUTION

•
•

•

Hitching The Trailer

2.

Failure to install the hitch pin before towing can result in
accidental opening of the coupler hitch latch which can lead to
the trailer coming off of the hitch ball causing serious damage,
injury or death. If pin will not fit into the front lower hole, the
coupler is not attached properly. Reset coupler on hitch ball.
A loose fit between the coupler and hitch ball can cause the
actuator and hitch ball to separate, causing serious damage,
injury or death. Check coupler every time prior to towing and
at each stop on long trips. Always make certain that coupler
latch safety pin is securely installed into coupler latch.
Never allow the coupler latch safety pin to remain in the
reverse lockout position hole. After reverse maneuvering,
always insert coupler latch safety pin back into coupler
latch. FAILURE TO REMOVE SAFETY PIN FROM REVERSE
LOCK OUT POSITION HOLE WILL PREVENT FORWARD
MOVEMENT BREAKING WHICH CAN RESULT IN SERIOUS
PROPERTY DAMAGE, INJURY OR DEATH.

3.

A minimum of 5% tongue weight and a maximum 10% tongue weight
of the trailer G.V.W.R must be located on the hitch ball. The Trailer
tongue should be parallel to the ground. Too much weight can cause
premature brake actuation and loss of control of the towing vehicle.
To little tongue weight can cause the trailer to fishtail, resulting
in loss of control of the tow vehicle and trailer (total trailer weight
G.V.W.R. includes weight of the trailer plus load).

1.

The vehicle, towing hitch and ball must have a rating equal to or
greater than trailer G.V.W.R..
DX6.6 will accept 2” balls only. Trailer balls larger than 2.00”
(50mm) or out of round will not fit the coupler or may result in
coupler failure. Balls smaller than 1.95” can cause shock loading
and sudden disconnection. Make certain ball latch is in correct
position to retain the hitch ball. Push latch until safety latch
engages plate below latch. Insert safety pin into forward hole as
a safety lock for the hitch ball coupler prior to towing. Do not tow
trailer if coupler is damaged.

CAUTION

CAUTION

The breakaway system is not designed to operate if the
trailer does not separate completely from the tow vehicle, or
if the tongue goes under the rear of the tow vehicle.
In the event that the breakaway system is used, check
all system components (cable, S-hooks, etc.) for proper
working order. Replace any damaged parts with genuine
Dexter parts only.
When resetting the break a way system keep hands and
fingers clear as you re-set the mechanism, hydraulic
pressure held in the system may cause the assembly to snap
back suddenly.

7.

Any control devices that restrict operation of the actuator cannot
be used. This includes certain sway control devices. The actuator
must be free to telescope in response to braking requirements.

8.

Equalizing or weight distributing hitches may be used, that are
designed to use with surge brake actuators, allow 6-8” free chain
length.

!

CAUTION

Failure to remove pin will also prevent forward braking. Pin must
be in the lower, forward hole as a safety lock for the hitch ball
coupler latch when towing at all times.

©2019 Dexter Axle Company | www.dexteraxle.com

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059-Z01-22 2019.10 | 08162-2/08057-2

9.

The actuator is designed for use with Free-Backing trailer brakes. To
block braking action, (in order to back up) with other types of brakes
including disc brakes, use an electric solenoid. For trailer movement
when brakes are not required, place the safety pin in the hole on the
side of the actuator housing to block movement of the actuator.

2.

To pump master cylinder, insert a flat tip screwdriver into the bleeding
access port on top, near the front of the actuator cover (1A).

3.

The screwdriver should be at the lowest angle possible to the
actuator so that it slides in front of the e-stop bracket (1B).

4.

Screwdriver tip MUST BE IN FRONT of the e-stop bracket and NOT
in the slot on the e-stop bracket (2A).

5.

Push the screwdriver forward and back to pump the master
cylinder. (2B).

Directions Vehicle Wiring - Brake Solenoid
1.

Disconnect trailer hitch and any wiring connectors from the vehicle.

2.

Connect a 14 gauge wire to the backup (reverse) light wire of the
vehicle. This wire should be of sufficient length to attach to the
existing vehicle/trailer wire receptacle. The end of this wire will
require a female end that will match the solenoid male connector
wire. Your vehicle may have a 5 wire connection for this purpose.

3.

For ease of use, tape or band the end of the reverse light wire to
the vehicle’s trailer electrical connector.

Maintenance

!

CAUTION

1B

The exterior of the actuator and brakes should always be rinsed with
fresh water after use in corrosive conditions. Before storing trailer,
clean brakes and repack the bearings. Failure to properly maintain
the actuator could cause serious damage, injury or death.
1.

Always check the brake fluid reservoir before using trailer. Make
sure it is at least half full. If not, re-fill to ³⁄₈” below the top of the
reservoir with DOT 3 brake fluid. Do not use DOT 5 brake fluid.
Check for leaks and repair as required. Never reuse brake fluid.

2.

To extend coupler and ball life, coat both with a thin coating of
grease. This will also eliminate squeaking. Wipe clean and renew
film each time trailer is used.

3.

Examine the actuator for bent parts or wear each time the trailer is
used. Replace parts as necessary.

4.

There are no user adjustments on the actuator.

5.

Actuator travel (shown by coupler roller path) over one inch
indicates a need to adjust the brakes or add fluid to the reservoir
or a need to bleed the brakes and check connections for leaks.
Adjust per instructions found in brake installation manual. In
general, back-off adjusters on drum brakes from locked position,
as required. Adjust Free-Backing brakes by rotating in forward
direction only. Failure to adjust may result in loss of braking. Disc
brakes do not require adjustment, check for pad wear.

2B

6.

The bleeding operation for that brake is complete when bubbling
stops. Be sure to tighten bleeder screw securely. Each wheel
cylinder must be bleed until all air is out of the lines. Replenish the
brake fluid during the bleeding process so the level does not fall
below half full level in the master cylinder reservoir.

7.

When bleeding and testing is completed, make sure master
cylinder is filled to ³⁄₈” below the top of the reservoir and filler cap
is securely in place.

Emergency Button Stop
Shown in normal operating position

Bleeding Instructions
1.

Bleeding
To bleed master cylinder and
Access PortFRONT
brakes, install FRONT
bleeder hose
on first wheel cylinder to be
bled; if tandem axle trailer,
FRONTaxle first, and the
FRONT
bleed farthest
farthest brake on that axle first.
Use a loose end of hose from
the bleeder valve submerged in a
glass container of brake fluid to
observe bubbling (hose must be
submerged into clean brake fluid to keep air from traveling back into
the brake cylinder). Loosen the bleeder screw located in the wheel
cylinder one turn, the system is now open to the atmosphere. Not to
be opened while pumping master cylinder.

©2019 Dexter Axle Company | www.dexteraxle.com

If button stop cable is showing DO NOT TOW TRAILER
Release emergency stop cable by prying spring out with a flat blade
screw driver.

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059-Z01-22 2019.10 | 08162-2/08057-2