ARB AIRLOCKER RD128 User manual

RD128
LAND ROVER, 24 SPLINE,
BANJO
AIR OPERATED
LOCKING DIFFERENTIAL
INSTALLATION GUIDE

No liability is assumed for damages resulting in the use of the information contained herein.
ARB AIR LOCKER Locking Differentials and AIR LOCKER are trademarks of ARB Corporation Limited.
Other product names used herein are for identification purposes only and may be trademarks of their respective owners.
ARB 4x4 ACCESSORIES
Corporate Head Office
42-44 Garden St Tel: [phone]
Kilsyth, Victoria Fax: [phone]
AUSTRALIA
3137
Australian enquiries [e-mail]
North & South American enquiries [e-mail]
Other international enquiries [e-mail]
www.arb.com.au

Table of Contents:
1
1 Introduction
3
1.1
Pre-Installation Preparation
3
1.2
Tool-Kit Recommendations
4
2 Removing the Existing Differential
5
2.1
Vehicle Support
5
2.2
Differential Fluid Drain
5
2.3
Removing of the Axles and Differential
5
2.4
Marking the Bearing Caps
6
2.5
Checking the Current Backlash Amount
7
2.6
Removing the Differential Carrier
8
3 Installing the Air Locker
9
3.1
Mounting the Ring Gear
9
3.2
Installing the Carrier Bearings
10
3.3
Drilling and Tapping the Bulkhead Port
11
3.4
Final Air Locker Assembly
12
3.5
Checking the Backlash
14
3.6
Installing the Seal Housing
15
3.7
Setting up the Bulkhead Fitting
17
3.8
Profiling the Seal Housing Tube
20
3.9
Bench Testing the Air Locker
22
3.10
Reinstalling the Differential & Axles
23
4 Installing the Air System
24
4.1
Mounting the Solenoid
24
4.2
Running & Securing the Air Line
26
4.3
Connection to the Bulkhead Fitting
27
5 Mounting & Connecting the Electrical System
29
5.1
Mounting the Actuator Switch(es)
29
5.2
Wiring the Actuator System
31
6 Testing & Final Assembly
34
6.1
Leak Testing
34
6.2
Testing the Air Locker Actuation
34
6.3
Filling the Differential
35
6.4
Post-Installation Check List
36
7 Parts List
37
7.1
Exploded Assembly Diagram
37
7.2
Itemized Parts List
38

2

3
IMPORTANT :
BEFORE ATTEMPTING TO DISMANTLE YOUR VEHICLE FOR THIS
INSTALLATION, PLEASE READ THIS INSTALLATION GUIDE IN ITS
ENTIRETY, AS WELL AS ALL APPLICABLE SECTIONS OF YOUR
VEHICLE MANUFACTURER’S SERVICE MANUAL.
1.1 Pre-Installation Preparation
This booklet is to be used in conjunction with your vehicle
manufacturer’s service manual. ARB endeavors to account for every
possible variation in vehicle model when publishing its installation
guides, and guides are updated regularly as new model information
becomes available, however, the rapid and globally varied release of
some vehicles makes it difficult to insure that your vehicle model has
been accurately accounted for. In the case of any technical
discrepancies between this guide and your service manual, we
strongly advise that you adhere to the specifications and techniques
as documented in your service manual.
Although your ARB Air Locker comes complete with all the step by
step instructions you will need to supplement your vehicle
manufacturer’s service manual and install your new differential, ARB
recommends that you have your Air Locker installed by a trained
professional. Many ARB distributors around the world have been fully
instructed in Air Locker installations by ARB, and have gained a wealth
of experience and skill from years of performing similar installations.
Once you begin this installation your vehicle will be immobile until all
steps of the installation are complete. Make sure your Air Locker kit is
the correct model for your vehicle and that it contains all of the parts
listed on back cover of this booklet. Also be sure you have
appropriately equipped yourself with all the necessary tools, parts, and
materials to complete this installation (see Section 1.2 Tool-Kit
Recommendations), and that you have allowed for an appropriate
amount of vehicle down time.
HINT : Place a mark inside each of the

symbols as
you complete each step. It is very important NOT to
miss any of the steps!

2 Removing the Existing Differential
4
1.2 Tool-Kit Recommendations
Below is a list of tools and supplies you may need to complete this
installation. Requirements for your vehicle may vary. Please consult
your vehicle service manual for additional recommendations.
1.2.1 Tools

Standard automotive sizes (metric and/or imperial) of sockets,
wrenches, Allan keys, and drills.

A dial indicator or other suitable measuring tool for checking ring &
pinion backlash.

An adjuster-nut wrench. (See your vehicle service manual.)

A razor knife suitable for cutting nylon tubing.

A torque wrench. (See your vehicle service manual for the required
torque range.)

A lubricant drain reservoir.

A 11.2mm [7/16”] drill and ¼”NPT tap for bulkhead fitting
installation.

An automotive bearing puller (2 jawed is recommended) or a
differential carrier bearing puller.

A bearing press or arbor press.
1.2.2 Supplies

Thread lubricant/sealant compound for pressure fittings
(e.g., LOCTITE #567 Teflon past)

Thread locking compound (e.g., LOCTITE #272)

A gasket sealant or replacement gasket for your third member.

A sufficient volume of differential oil to completely refill your
housing. (See the ARB Air Locker Operating and Service Manual
for recommended lubricants)

A soap and water mixture to test for air leaks.

2 Removing the Existing Differential
5
2.1 Vehicle Support

Safely secure the vehicle on a hoist. We recommend supporting the
vehicle on a chassis hoist to keep the differential area at a
convenient working height and to leave the wheels and axles free
to be rotated and removed.

Once supported off the ground, release the parking brake and
leave the vehicle in neutral. Chock the wheels if necessary.
2.2 Differential Fluid Drain

Clean around the differential drain plug to prevent dirt from entering
the differential.

Position a fluid drain reservoir under the differential and loosen the
differential drain plug.

Completely drain all differential fluid.
HINT : This is a good time to check for metal particles in
your oil and in the bottom of the housing which may
indicate a worn bearing or differential component.
2.3 Removal of the Axles and Differential

Remove the axles according to your vehicle’s service manual.

Disconnect the drive shaft from the flange of the differential.

Remove the third member from the differential housing. Refer to
your vehicle’s service manual.
IMPORTANT :
Collision damage or heavy off-road use of your vehicle in the past may
have resulted in some degree of bending in the axle. Any misalignment
of the axle tubes may result in excessive wear and/or failure of your
differential and axle shafts. ARB strongly recommends that you have
your axle assembly inspected for concentricity and straightness before
installing your Air Locker.

2 Removing the Existing Differential
6
2.4 Marking the Bearing Caps

Using a small pointed center punch, gently mark the bearing caps
in a way that will enable you to know which cap is ‘LEFT’ and which
cap is ‘RIGHT’, which way is ‘UP’ and which way is ‘DOWN’.
(Fig.1.)

Mark the right hand cap in a similar way.
HINT : Many installers choose to make one punch mark on
the left hand side of the left hand bearing cap and a
similar mark on the housing at close proximity to the
cap mark. The right hand side is then designated with
two punch marks on the right hand side of the cap and
two similar punch marks on the housing.
Figure 1.

2 Removing the Existing Differential
7
2.5 Checking the Current Backlash Amount
IMPORTANT:
This step is a precautionary measure recommended by ARB due
to the fact that some after market ring and pinion sets have been
manufactured to run with different backlash settings than those
specified by your vehicle manufacturer. Although ARB must
recommend you set backlash according to your service manual
guidelines, we also advise that you compare the backlash
measurements taken here to the recommended backlash settings
in your vehicle service manual. Measurements found to be
outside of your service manual recommendations may indicate
the need to deviate from those settings in order to achieve quiet
running with a good contact mark.
Refer to your vehicle service manual or your local authorized
ARB installer for more information.

Set a dial indicator on one of the ring gear teeth. (Fig.2.)
Figure 2.

While supporting the pinion gear by holding the pinion flange, rotate
the differential in both directions while observing the maximum
variation in depth from the indicator (i.e., the highest value minus
the lowest value). This value is referred to as the ring and pinion
backlash.

Rotate the differential center 90°and measure again for accuracy.

Record the average of all measurements.

2 Removing the Existing Differential
8
2.6 Removing the differential carrier

Remove the adjuster nut locking tabs.

Remove the bearing caps from the third member.

Remove the adjuster nuts.

Carefully remove the differential carrier from the third member.

Remove the tapered roller bearings from the differential carrier with
a bearing puller. (Fig.3.)
HINT : Check the condition of the bearing for wear and
replace if necessary.
Figure 3.

3 Installing the Air Locker
9
3.1 Mounting the Ring Gear

Remove the bolts that hold the ring gear in place.

Using a plastic or copper hammer, tap in a circle around the ring
gear to separate it from the differential carrier.

Thoroughly clean any thread locking compound or other foreign
matter from the holes of the ring gear, the threads of the ring gear
bolts, the mating surfaces of the ring gear and the Air Locker
flange.
HINT : Rubbing the ring gear mounting face with a flat oil
stone before installation will remove any high spots
around the threads.

Heat the ring gear to between 80 and 100°C (175 - 212°F) in hot
water or in an oven to slightly expand the gear and facilitate
assembly.
NOTE : NEVER HEAT GEARS WITH A FLAME! This could
damage the hardened surface of the gear and result in
premature wear or failure.

Dry the gear and tapped holes with compressed air (if wet).

Apply a thin film of high-pressure grease to the ring gear shoulder
of the Air Locker to prevent seizing.

Install the ring gear onto the Air Locker by aligning the tapped holes
and then gently tapping it around in a circle with a soft mallet or
hammer. Avoid using the bolts to pull the ring gear down as this
puts excess strain on the bolts and the differential flange.

Apply a thread locking compound to the thread of each ring gear
bolt before inserting it. Do not apply locking compound directly into
the threaded hole as this could prevent the bolt from reaching its
full depth.
NOTE : On some models, the crown wheel bolts cannot be
reused and should therefore be replaced. Refer to
your vehicle manufacturer’s service manual for
details.

Tighten the ring gear bolts in a star pattern with a torque wrench
(Fig.4.) set to your vehicle manufacturer’s specified torque.

3 Installing the Air Locker
10
Figure 4.
3.2 Installing the Carrier Bearings

Apply a thin film of high pressure grease to the bearing journals of
the Air Locker, then press the bearing cones onto the bearing
journals as shown in figure 5.
Figure 5.

3 Installing the Air Locker
11
3.3 Drilling and Tapping the Bulkhead Port
An air line port must be drilled and tapped through the differential
housing to mount the bulkhead fitting into.

Mark a spot on the left hand side (opposite the ring gear) toward
the top of the differential housing that is in an area well clear of the
differential, the ring gear, and any other obstructions that could
snag the seal housing tube. (Fig.6.)
Figure 6.

Cover the drive pinion area with a rag to protect it from metal filings.

Secure the differential housing to the work bench.

Drill an 11.2mm [7/16”] diameter hole through the differential
housing square to the outside surface.

Tap the hole from the outside using ¼”NPT thread tap.

Remove any sharp edges that may chip off from around the hole
and fall into the housing.

Very carefully, remove the rags and inspect with a service light
inside the housing to insure no metal filings are left behind.
HINT : Placing a magnet on the inside of the housing near
the hole will help to catch any debris from drilling and
tapping.

3 Installing the Air Locker
12
3.4 Final Air Locker Assembly

Clean all parts of the differential assembly, paying particular
attention to the seal housing journal.

Place the Air Locker into the differential housing and install the
bearing caps.
NOTE : Be sure to check that the bearing caps are on the
correct sides of the third member and are correctly
aligned.

Insert the bearing cap bolts and hand tighten.
NOTE : Before attempting to install the adjuster nuts, make
sure the threads on the inside of the bearing caps and
differential housing are perfectly aligned. If they are
not, the threads could be stripped.

Insert and lightly hand tighten the adjuster nut supplied with the Air
Locker kit into the ring gear side bearing cap.
NOTE : You should feel no backlash between the ring and
pinion gears once the adjuster nut tightens.
IMPORTANT:
On Land Rover differentials that utilize roll pins to hold the
adjuster nuts in place, use Loctite 272 on the threads of the
supplied Air Locker adjuster nut when installing it.

Reverse the adjuster nut (counterclockwise) ¼ turn.
NOTE : Assembly space in some Land Rover differentials has
been found to vary slightly. Using an automotive
feeler gauge, check that some clearance exists
between the bearing cap and the Air Locker
(Figure 7.). Rotate the differential one full turn while
checking. If any part of the Air Locker contacts the
bearing cap then the cap should be removed and any
contact points should be filed or ground until some
assembly clearance exists.

3 Installing the Air Locker
13
Figure 7.

Insert the original adjuster nut onto the opposite side of the
differential and tighten with the appropriate adjuster nut wrench.
NOTE : You should now feel some backlash between the ring
and pinion gears. If not, there might be a clearance
problem which is binding the carrier. Re-check the
clearance.
CLEARANCE REQUIRED

3 Installing the Air Locker
14
3.5 Checking the Backlash

Set a depth indicator on one of the ring gear teeth (Fig.8.).

While supporting the pinion gear by holding the drive shaft flange,
rotate the differential in both directions while observing the
maximum variation in depth from the indicator (i.e., the highest
value minus the lowest value). This value is referred to as the ring
and pinion backlash.

Rotate the differential center 90°and measure again for accuracy.

Refer to your vehicle service manual for the specified maximum
and minimum amounts of backlash.
IMPORTANT:
It is critical to set up bearing pre-load when a differential is
installed. Improper pre-load will result in undue bearing wear,
increased stresses in the differential center, increased running
noise, and ultimately, ring and pinion gear damage.

Adjust the backlash and pre-load using an adjuster nut wrench to
tighten or loosen the adjuster nuts as required. (Refer to your
vehicle service manual.)

Recheck backlash as before, repeating this procedure until
backlash is within the specified amount.

Tighten the bearing cap bolts with a torque wrench to the torque
specified in your vehicle manufacturer’s service manual.
Figure 8.

3 Installing the Air Locker
15
3.6 Installing the Seal Housing

Make sure the grooves and airway of the seal housing are clean
and free from any contaminants (e.g. water, dirt, metal filings, etc.).

Inspect the seal housing O-rings (supplied) for dirt, damage or
other conditions which might cause leaks.

Generously lubricate the O-rings with oil prior to assembly, then
insert them into the grooves of the seal housing.
NOTE : When assembling the O-rings, be careful not to leave
them twisted when seated in the grooves as this could
cause excessive wear and leakage.

Lubricate the seal housing running surface on the Air Locker carrier
with oil.

Carefully install the seal housing by sliding it all of the way onto the
bearing journal with a gentle twisting motion until it sits flat against
the adjuster nut.
NOTE : A twisting motion (i.e., a slight rotation while pressing
the seal housing on) will allow the O-rings to engage
gently and prevent them from twisting. Twisted
O-rings will result in pre-mature O-ring wear and oil
contamination in the air system due to the helical
shape formed by the O-ring mould line.

Rotate the seal housing until the square cutout lines up with the
locking tab position at the center of the bearing cap, and then
assemble the locking tab. The locking tab must not come into
contact with the seal housing. (Fig.9.)
Figure 9.

3 Installing the Air Locker
16
3.6.1 Roll Pin Type

If your diff has roll pins instead of locking tabs, slightly rotate the
adjuster nut so that the roll pin is in the center of one of the adjuster
nut teeth as shown. When installing the roll pin, knock it down
making sure that it will not contact the seal housing (Fig. 10.).
Figure 10.
3.6.2 Hook Type

It may be necessary to modify the locking tab in order to clear the
seal housing by grinding or filing a small flat on the end. (See
Fig.11.)
Figure 11.
GRIND HERE

3 Installing the Air Locker
17

Install the spring clip by first hooking both ends of the clip into the
small aligned cutouts of the seal housing and the adjuster nut, and
then snapping the clip into the groove of the seal housing using a
screwdriver. (Fig.12.)
Figure 12.

Check that the seal housing is now secured from rotating and that it
is still sitting flat against the adjuster nut.
3.7 Setting up the Bulkhead Fitting

Apply thread sealant to the threads of the bulkhead body.

Screw the bulkhead body into the tapped hole, and tighten.

Wipe the area clean of any excess thread sealant (inside and
outside of the housing).

Without using sharp, jagged tools such as pliers (your hands are
the best tool for this job), bend the seal housing tube on the outside
of the housing to approximate the finished profile. This will allow the
tube to be trimmed to a length that would allow it to protrude from
the bulkhead fitting. (See Fig.13.)
IMPORTANT:
The seal housing must still be able to freely float on the seal
housing journal after the tube is connected to the bulkhead
fitting. Therefore, it is critical to ensure that the tube is not under
any tension. To avoid this always leave the tube long enough so
that a hook shape can be formed between the seal housing and
the bulkhead.

3 Installing the Air Locker
18
NOTE : Use an automotive brake line tubing cutter to cut the
seal housing tube, never a hacksaw as this will leave
metal filings in the air system.
Figure 13.

From the inside of the housing, insert the trimmed tube into the
bulkhead.

From the outside of the housing, assemble the small O-ring over
the top of the short length of seal housing tube protruding through
the bulkhead fitting.

While holding the seal housing tube into the bulkhead fitting, insert
the small drilled end of the center compression nut over the
extended tube as shown in the assembly diagram (Fig.14.), and
screw it into the bulkhead body, and lightly tighten.