Airlocker RD155 User manual

RD155
MITSUBISHI 9.5”,
33 SPLINE, IRS
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 and 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 the Axles and Differential
5
2.4
Marking the Bearing Caps
6
2.5
Checking the Current Backlash Amount
6
2.6
Spreading the Differential Housing
8
3 Bench Measurement
9
3.1
Approximate Backlash Shimming
9
3.2
Calculation & Selection of Shims
11
4 Installing the Air Locker
12
4.1
Installing the Carrier Bearings
12
4.2
Mounting the Ring Gear
12
4.3
Assembling the Seal Housing
13
4.4
Calculation & Selection of Pre-Load Shims
14
4.5
Drilling and Tapping the Bulkhead Port
16
4.6
Final Air Locker Assembly
17
4.7
Final Backlash Checking
17
4.8
Profiling the Seal Housing Tube
18
4.9
Setting up the Bulkhead Fitting
20
4.10
Bench Testing the Air Locker
22
4.11
Reinstalling the Differential and Axles
23
5 Installing the Air System
24
5.1
Mounting the Solenoid
24
5.2
Running & Securing the Air Line
26
5.3
Connection to the Bulkhead Fitting
27
6 Mounting & Connecting the Electrical System
28
6.1
Mounting the Actuator Switch(es)
28
6.2
Wiring the Actuator System
29
7 Testing & Final Assembly
32
7.1
Leak Testing
32
7.2
Testing the Air Locker Actuation
32
7.3
Filling the Differential
33
7.4
Post-Installation Check List
34
8 Parts List
35
8.1
Exploded Assembly Diagram
35
8.2
Itemized Parts List
36

2

1 Introduction
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!

1 Introduction
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, Allen keys, and drills.

A dial indicator or other suitable measuring tool for checking ring &
pinion backlash.

A standard automotive feeler gauge.

Automotive brake tubing cutters to cut the copper tubing.

A razor knife to cut the nylon tubing.

A differential housing spreader, to facilitate removal of the carrier.

A torque wrench. (See vehicle service manual for required torque
range.)

A lubricant drain reservoir.

Suitable measuring tools to measure a differential for pre-load
and/or backlash shimming. (See Section 3 Bench Measurement)

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 paste)

Thread locking compound (e.g., LOCTITE #272)

Either a replacement gasket, or gasket sealant.

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.

A selection of differential bearing shims to set-up pre-load and
backlash. (See section 3 Bench Measurement)

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

Position a fluid drain reservoir under the differential.

Remove fluid drain plug to empty all differential oil.
HINT : This is a good time to check for metal particles in
your oil which may indicate a worn bearing or
differential component.
2.3 Removing the Axles and Differential

Remove the axles as per your vehicle’s service manual.

Disconnect the drive shaft from the flange of the differential.

Remove the differential from the vehicle. (Refer to your vehicle’s
service manual)
NOTE : The differential housing is heavy and quite difficult to
handle when covered in oil. Do not drop it!
NOTE : Check the axle shaft oil seals for signs of wear or
damage, and replace if necessary.

2 Removing the Existing Differential
6
2.4 Marking the Bearing Caps

Remove the inspection cover.

Using a pointed center punch, gently mark the differential housing
and the bearing caps in a way that will enable you to correctly
position the cap during reassembly. (Fig.1.)
Figure 1.
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.

2 Removing the Existing Differential
7

Set a depth indicator on one of the ring gear teeth as in Figure 2.
Figure 2.

While supporting the pinion gear by holding the drive shaft, 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 Spreading the Differential Housing
IMPORTANT:
Spreading the differential housing with a differential case
spreader is a step which 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.

Unbolt and remove the bearing caps.

Setup the differential spreader and a dial indicator and carefully
spread the differential housing (Fig.3.) just enough to remove the
differential carrier (Refer to your vehicle’s service manual).
NOTE : Never spread the housing more than 0.5mm [0.020”].

Once the housing has been adequately spread, the differential may
be removed by pulling forward on the differential center.

Remove spreader tension.
Figure 3.

3 Bench Measurement
9
3.1 Approximate Backlash Shimming
In order to reproduce a similar pre-load and ring and pinion backlash
in your Air Locker to that of your original differential, measurements
need to be taken so that a shim thickness can be calculated.

Secure the original differential to a work bench.

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.

Remove the original bearings and shims from the differential center
using a bearing puller.
NOTE : Keep the bearings and shims separated so that they
can be identified as to which end of the differential
they came from.

Examine the bearing cups and cones from Figure 4. for damage or
wear and, if necessary, discard them and replace with the same
size and type of bearings.
Figure 4.

3 Bench Measurement
10

Using a caliper or similarly accurate measurement method
(i.e., able to take accurate measurements within 0.04mm [0.0015”]),
measure the distance from the shoulder of the bearing journal to
the ring gear mounting face (shown as ‘A’ in Fig.4.) and record this
measurement as ‘A’.

Measure the thickness of the factory shim removed from the end of
the differential carrier (shown as ‘B’ in Fig.4.) and record this
measurement as ‘B’.
Figure 5.

Measure the distance from the Air Locker bearing shoulder to the
ring gear mounting face (shown as ‘C’ in Fig.5.) and record this
measurement as ‘C’.

3 Bench Measurement
11
3.2 Calculation & Selection of Shims
Ideally, the measurement you recorded as ‘C’ from the Air Locker
differential will closely match ‘A’ on the existing differential (within
0.1mm [0.004”] ) and then the factory shim can be reused, however,
quite often these measurements will vary slightly between one factory
differential and the next.
If this is the case you must create a new shim pack thickness by using
the measurements you recorded earlier to find a desired measurement
for ‘D’ in Figure 5.
Use the following calculation:
A + B – C = D (Replacement Shim Pack)
HINT : If your calculations are correct then the following
equation will also be true:
A + B – C – D = ZERO

Create a shim pack to match the thickness calculated as ‘D’.
To achieve the desired shim thickness you can:
•Machine down the factory shim thickness.
•Add shims between the factory shim and the bearing cup.
HINT : A selection of shims of this size have been supplied
with your Air Locker kit.
•Purchase new factory shims at the desired thickness.
•Use a universal shim kit available from most drive train
specialists.
NOTE : NEVER machine the Air Locker.

4 Installing the Air Locker
12
4.1 Installing the Carrier Bearings

With the Air Locker well supported in an arbor press, apply a thin
film of high pressure grease to both bearing journals.

Press one of the tapered roller bearing cones onto one of the
bearing journals of the Air Locker until the bearing seats firmly
against the bearing journal shoulder.

Invert the Air Locker and press the second bearing cone onto the
opposite bearing journal until the bearing seats firmly against the
bearing journal shoulder.
NOTE : Never re-use any bearings which are damaged or
worn.
4.2 Mounting the Ring Gear

Apply a thin film of high-pressure grease to the ring gear shoulder
of the Air Locker to prevent seizing.

Thoroughly clean any thread locking compound or other foreign
matter from the holes of the ring gear, the threads of the ring gear
bolts, and the mating surfaces of the ring gear and the Air Locker
flange.
NOTE : 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 an
oven or in hot water 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 ring gear with compressed air (if wet), paying particular
attention to the threaded holes.

Install the ring gear onto the Air Locker by aligning the holes in the
flange with the tapped holes in the ring gear, then gently tapping it
around in a circle with a plastic or copper hammer.

4 Installing the Air Locker
13
NOTE : Avoid using the bolts to pull down the ring gear 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.
NOTE : Do not apply threading compound directly into the
threaded hole as this could prevent the bolt from
reaching its full depth.

Tighten the ring gear bolts in a star pattern with a torque wrench
according to your vehicle manufacturer’s specified torque.
4.3 Assembling the Seal Housing
Figure 6.

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.

4 Installing the Air Locker
14

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. Assemble the bearing cup onto the left-hand side of the Air
Locker.

Carefully install the seal housing by sliding it all of the way onto the
bearing journal with a gentle twisting motion. This will allow the O-
rings to engage gently.
4.4 Calculation & Selection of Pre-Load Shims
In order to pre-load the tapered roller bearings in your Air Locker,
measurements need to be taken so that a value can be calculated for
the shim thickness ‘E’ in Figure 6.

Hold the bearing cup and shim pack ‘D’ (Fig.5.) in place, and insert
the Air Locker into the housing. Ensure that the seal housing tube is
positioned in line with the oil groove in the housing (Fig. 7.).

Push the Air Locker hard across against the bearing and shim pack
‘D’, and measure the gap between the end of the seal housing and
the bearing seat of the differential housing with a feeler gauge.
Figure 7.
OIL
GROOVE

4 Installing the Air Locker
15

Consult your vehicle manufacturer’s service manual to determine
the carrier bearing pre-load amount specified for your vehicle.
NOTE : If your service manual specifies preload in terms of a
torque value measured off the drive pinion flange,
then assume a preload amount of 0.25mm [0.01”] for
the following calculations. Once you have assembled
the housing to check the final backlash (Refer to
Section 4.7 Final Backlash Checking) you should
verify that your preload is correct using a torque
wrench and your service manual’s table of values.

Add the specified pre-load amount to the measurement taken with
the feeler gauge to determine a shim amount for ‘E’ in Figure 6.
PRE-LOAD + END FLOAT = SHIM PACK
NOTE : Ideally, the measurement you recorded as ‘E’ from the
Air Locker differential will closely match the OE
Master Shim (within 0.1mm [0.004”] ) and then the
factory shim can be reused, however, quite often
these measurements will vary slightly between one
factory differential and the next.

Use the left hand factory master shim and/or select suitable shims
from the shim kit supplied with your Air Locker to make up a shim
pack of this thickness. (Refer to section 3.2 for methods of shim
adjustment).

Cut a slot into shim pack ‘E’ as clearance for the seal housing tube
at final assembly. Figure 8. shows the desired size of the slot.
Figure 8.

Remove any sharp or protruding edges from around the notch, and
place it on the end of the seal housing, making sure that you line
the slot up with the tube.

4 Installing the Air Locker
16
4.5 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 exterior of the differential housing toward the top
in an area that will be well clear of the Air Locker body, the ring
gear, and any other obstructions that could snag the seal housing
tube. (Fig.9.)
Figure 9.

Remove the Air Locker from the differential housing.

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.

4 Installing the Air Locker
17
4.6 Final Air Locker Assembly

Spread the differential housing again (Refer to section 2.6).

Hold shim packs ‘D’ (Refer to section 3.2) and ‘E’ (Refer to section
4.4) in position on the Air Locker ensuring to line up the seal
housing tube with the slot in shim pack ‘E’.

Reinstall the Air Locker into the differential housing, once again
ensuring to line up the seal housing tube with the oil groove (Fig.
7.).
NOTE : If the carrier is too difficult to install with the added
shim pack then the spreader tension may need to be
increased. Do not spread the housing more than
0.50mm [0.020”].

Place the bearing caps in place, making sure that there is no
contact between the bearing cap, master shim and seal housing
tube.

Relieve all tension on the housing spreader.

Tighten all bearing cap bolts with a torque wrench to the torque
specified in your vehicle manufacturer’s service manual.
4.7 Final Backlash Checking

Set a depth indicator on one of the ring gear teeth as in Figure 10.

While supporting the pinion gear by holding the drive 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.
Figure 10.

4 Installing the Air Locker
18

Refer to your vehicle service manual for the specified maximum
and minimum amounts of backlash. If the backlash is not within the
specifications then the differential will have to be removed and re-
shimmed.
4.7.1 Re-Shimming the Backlash
NOTE : This step is only necessary when adjusting for
incorrect backlash.

Reapply the spreader to the differential housing.

Remove the bearing caps.

Remove the differential.

To increase the amount of backlash, reduce the shim thickness ‘D’
(Fig.5.) and increase the shim thickness ‘E’ (Fig.6.) by the same
amount. Reverse this step to decrease the backlash.

Remount the differential as before.

Release spreader tension.

Check backlash again as before.
4.8 Profiling the Seal Housing Tube

Without using sharp, jagged tools such as pliers (usually your
hands are the best tool for this job), bend the seal housing tube so
that it closely follows the profile of the differential housing and
protrudes through the bulkhead port in the differential housing (refer
to Fig.11., 12., & 13.).

Trim the tube to length using automotive brake line cutters.

Run the seal housing tube between the bearing cap, the differential
housing, and the cover plate and out of the bulkhead port.

Check that the contour of the tube will not interfere with the Air
Locker, the ring gear, the master shim, the bearing cap, or the
cover plate.