M-652-001 Service Bulletin/Repair Instructions

Axle Alignment Specifications

M-652-001

(March 2009)
Valid for

ALL CXU, CHU, GU, TD, MRU, LEU
Case description

This service bulletin provides the latest Mack axle alignment specifications.

Note: For vehicles equipped with the MACK RSA (Road Stability Advantage) program (Bendix® ABS-6 Advanced with

ESP® [Electronic Stability Program]), any adjustments to vehicle alignment require recalibration of the steering angle

sensor. For information, refer to the Bendix® Service Data Sheet (SD-13- 4869). This data sheet can be obtained by

visiting the Bendix® website at www.bendix.com.

Note: Does not apply to Mack Trucks Australia
Caster

All measurements must be taken with the vehicle in an unloaded condition, and the steering axle and drive axles on a

level surface. RH and LH caster readings must not vary more than 0°30′ (.5°).

Caster Specifications

Single Non-Driving Front Axle — Power Steering

MRU, LEU, LE, MR, CV, CL, RD, RB, DM, DMM

models
4° to 6°
CH models prior to 12/9/96
1° to 3°
CXU, CHU, GU, TD, CXP, CXN, CHN, CTP, CT, CX

models and CH models after 12/9/96
3° to 5°
Single Non-Driving Front Axle — Manual Steering

All model except those equipped with ArvinMeritor™

front axles
1° to 3°
All Models equipped with ArvinMeritor™ Front Axles

(Excluding CH Models)
0° to 2°
CH Models equipped with ArvinMeritor™ Front Axles
1° to 3°
AIRTEK® 12, 13.2 and 14.6 Front Axles*

Left Side
3.75° +1°/ -0.5°
Right Side
3.75° +1°/ -0.5°
Cross Caster
0° to maximum 1.5°
Single Front Driving Axle (Except Marmon Herrington

(MT23) after January 1, 1995
3°30′ to 5°30′ (3.5° to 5.5°)
Marmon Herrington Front Driving Axle (MT23) After

January 1, 1995
2°30′ to 4°30′ (2.5° to 4.5°)
Two Front Axles

Front Driving Axle
3°30′ to 5°30′ (3.5° to 5.5°)
Non-Driving Front-Front Axle
4° to 6°
Non-Driving Rear-Front Axle
4°30′ to 6°30′ (4.5° to 6.5°)
* On chassis equipped with AIRTEK® front axles, it is critical that caster be measured with the vehicle at the

correct ride height. For information on measuring and adjusting ride height, and for any other information

concerning the AIRTEK® front axle, refer to the Hendrickson Technical Procedure Manual, AIRTEK® Service

Instructions for MACK Vehicles, manual No. 17730-250.

Specifications for vehicles built prior to 1993 may be different. See previously published information, or alignment

equipment manufacturer's charts for specifications on older vehicles.
Camber

All measurements must be taken with the vehicle in the unloaded condition.

Camber Specifications

Vehicles Built after January 1, 1995 (with MACK Front Axles)

MACK Non-Driving Front Axles:

FXL 12, 14.6, 18, 20 and 23
1/4° ± 7/16° (0.25° ± 0.43°
FAW 10.5, 12 and 14.3
0° ± 7/16° (0° ± 0.43°)
FA(W) 18 and 20
1/4° ± 7/16° (.25° ± 0.43°)
FA23
3/4° ± 7/16° (.75° ± 0.43°)
Vehicles Built Prior to January 1, 1995 (with MACK Front Axles)

MACK Non-Driving Front Axles (Except FA23)
0° to 0°30′ (0° to 0.5°)
MACK FA23 Non-Driving Front Axle
0°30′ to 1° (.5° to 1°)
AIRTEK® 12, 13.2 and 14.6 Front Axles

Left Side
0° ± 0.5°
Right Side
0° ± 0.5°
Cross Camber
0° to maximum 1°
Eaton/Dana Non-Driving Front Axles:

EFA-12F4, EFA-13F5 and EFA-20F4 Axles

Left Side
7/16° ± 7/16° (.43° ± 0.43°)
Right Side
−1/16° ± 7/16° (−.06° ± 0.43°)
E1202I Axles

Left Side
1/8° ± 7/16° (.13° ± 0.43°)
Right Side
−1/8° ± 7/16° (−.13° ± 0.43°)
Eaton/Dana Non-Driving Front Axles:

I-120

Left Side
−1/8° ± 7/16° (−.13° ± 0.43°)
Right Side
−1/8° ± 7/16° (−13° ± 7/16)
ArvinMeritor™ Non-Driving Front Axles
−0°41′ to 0°11' (−.69° to 0.19°)
Driving Front Axles:

ArvinMeritor™
0° to 0°30′ (0° to 0.5°)
FABCO (SDA23, 20B, 18B and 16)
0°15′ to 0°45′ (.25° to 0.75°)
Marmon-Herrington (MT23)
0°24′ to 0°36′ (.4° to 0.6°)
Toe
Set toe toward zero side of specification on vehicles equipped with steel-belted radial tires or vehicles with lightly

loaded front axles.

Toe Specifications

MACK Non-Driving Front Axles:

FAW10.5, 12, 14.3, FA(W)18, 20, FA23, FXL12, 14.6,

18, 20
1/16″ ± 1/32″ (.06″ ± 0.03″)

or

0.07° ± 0.035°

or

1.5 mm/m ± 0.75 mm/m
AIRTEK® 12, 13.2 and 14.6 Front Axles
1/16″ +0"/ -1/16" (.06″ +0"/ -.06″)

or

0.07° +.00°/ -.07°

or

1.5 mm/m +0/ -1.5 mm/m
ArvinMeritor™, Eaton/Dana Non-Driving Front Axles
1/16″ ± 1/32″ (.06″ ± 0.03″)

or

0°4′ ± 0°2′ (0°2′ to 0°6′)

or

.07° ± 0.03° (.03° to 0.10°)

or

1.5 mm/m ± 0.75 mm/m
ArvinMeritor™ and Marmon Herrington Front Driving

Axles
1/16″ ± 1/16″ (.06″ ± 0.06″)

or

0°4′ ± 0°4′ (0° to 0°8')

or

.07° ± 0.07° (0° to 0.14°)

or

1.5 mm/m ± 1.5 mm/m
TOE-OUT*

FABCO Front Driving Axles (SDA23, 20B, 18B and 16) 1/16″ ± 1/16″ (.06″ ± 0.06″)

or

0°4′ ± 0°4′ (0° to 0°8')

or

.07° ± 0.07° (0° to 0.14°)

or

1.5 mm/m ± 1.5 mm/m
* HUNTER Alignment equipment measurements indicating toe-out will be a negative number, e.g., −.07°
Thrust

Specifications for Thrust Angles on Rear Drive Axles:

Thrust Specifications

Adjustable Suspensions
0″ ± 1/8″ (0″ ± 0.125″)

0° ± 0.08°

0 mm/m ± 1.4 mm/m
Non-Adjustable Suspensions
0″ ± 1/4″ (0″ ± 0.25″)

0° ± 0.16°

0 mm/m ± 2.8 mm/m
Scrub (Parallelism)

Specifications for Scrub (Parallelism) on Rear Drive Axles:

Thrust Specifications

Adjustable Suspensions
0″ ± 1/8″ (0″ ± 0.125″)

0° ± 0.08°

0 mm/m ± 1.4 mm/m
Non-Adjustable Suspensions
0″ ± 1/4″ (0″ ± 0.25″)

0° ± 0.16°

0 mm/m ± 2.8 mm/m
Axle Alignment

The following specifications have been established for axle alignment on a MACK vehicle under chassis only

conditions in order to achieve the optimum in tire wear and subsequent customer satisfaction. Before taking

measurements, always drive the vehicle back and forth in a straight line four or five times. Where distance is limited,

at least the length of the chassis should be travelled. This operation must be performed to ensure that the suspension

has not taken a set.
Centring Rear Axles (Chassis Equipped with SS Suspensions)

The first step in axle alignment is the centring of rear axles. To accomplish this, a measurement must be made

between the frame and the brake drums on each axle. A convenient extension straightedge can be made from a

straight piece of steel bar stock and attached to the frame rail with magnets. With a tape measure, measure from the

straightedge to the brake drum at the three designated points shown in the illustration below.

Straightedge to Tire Measuring Points (SS Suspension Shown)
The maximum allowable difference between the measurements taken at the front-rear and rear-rear brake drums to

the straightedge must not exceed 6.4 mm (1/4 inch), whether or not the chassis is equipped with a transverse torque

rod.

The maximum allowable difference between the left- and right-hand sides on the same axle, front-rear or rear-rear

must not exceed 6.4 mm (1/4 inch) if the chassis is equipped with a transverse torque rod, or 12.7 mm (1/2 inch) if the

chassis is NOT equipped with a transverse torque rod.
Centring Rear Axles (Chassis Equipped with AL Suspension and FixedLength Transverse Torque Rods)

The first step in proper axle alignment is verifying that the rear axles are properly centred on the chassis. Before any

alignment measurements are taken, the chassis should be driven back and forth in a straight-line several times to

allow the suspension to move into its normal operating position. To verify that the rear axles are centred, perform the

following steps:

1. With the chassis parked on a level surface, block the front wheels to prevent the vehicle from moving, then

release the parking brakes. (Air system pressure should be between 110 psi to 130 psi when performing these

procedures.)

2. Measure the ride height. Ride height gauges are available to accurately measure chassis ride height. Refer to

service bulletin SB136012 for information on using the gauges, and for a list of gauge part numbers.

Note: For information concerning measuring and adjusting ride height, refer to the MACK AL and AL II Air

Suspension Service and Repair Manual, 14–101, for AL, AL II and AL-401LH suspensions, and the MAXAIR™

40 Air Suspension Service and Repair Manual, 14–102, for the MAXAIR™ 40 (AL-405) suspensions.

Note: Beginning approximately 3/19/01, a change in the spring seat and spacer resulted in a ride height

dimension change from 5-1/ 4″ to 4-7/8″ on MAXAIR™ 40 air suspensions. Suspensions having a ride height of

4-7/8″ are identified by an “X” marking on the spring cap. Always look for the “X” marking before adjusting ride

height. (Refer to service bulletin SB136010.)

3. After the ride height has been checked and/or adjusted, determine if the axles are centred by measuring from

the outside of the frame rail to the inside edge of the spring clip (U-bolt) (Dimension “A” in the illustration

below). The maximum allowable side-to-side difference on any one axle is 6.34 mm (1/4 inch). Washer spacers

(part number 37AX271) can be added or removed from either side of the torque rod in order to obtain the

correct axle positioning. (Refer to the figures below.)

Rear Axle Alignment — MACK AL Suspension with Fixed-Length Transverse

Torque Rods
4. After axle centring is verified or corrected, exhaust the air from the suspension and verify that no interference

exists between the frame rail and any spring clip (U-bolt).
Centring Rear Axles (Chassis Equipped with AL Suspension and

Adjustable Transverse Torque Rods)

The first step in proper axle alignment is verifying that the rear axles are properly centred on the chassis. Before any

alignment measurements are taken, the chassis should be driven back and forth in a straight-line several times to

allow the suspension to move into its normal operating position. To verify that the rear axles are centred, perform the

following steps:

1. With the chassis parked on a level surface, block the wheels to prevent the vehicle from moving, then release

the parking brakes. (Air system pressure should be between 110–130 psi when performing these procedures.)

2. Measure the ride height. Ride height gauges are available to accurately measure chassis ride height. Refer to

service bulletin SB136012 for information on using the gauges, and for a list of gauge part numbers.

Note: For information concerning measuring and adjusting ride height, refer to the MACK AL and AL II Air

Suspension Service and Repair Manual, 14–101, for AL, AL II and AL-401LH suspensions, and the MAXAIR™

40 Air Suspension Service and Repair Manual, 14–102, for the MAXAIR™ 40 (AL-405) suspensions.

Note: Beginning approximately 3/19/01, a change in the spring seat and spacer resulted in a ride height

dimension change from 5-1/4″ to 4-7/8″ on MAXAIR™ 40 air suspensions. Suspensions having a ride height of

4-7/8″ are identified by an “X” marking on the spring cap. Always look for the “X” marking before adjusting ride

height. (Refer to service bulletin SB136010.)

3. After ride height has been checked and/or adjusted, determine if the axles are centred by measuring from the

outside of the frame rail to the inside edge of the spring clip (U-bolt) (dimension “A” in the illustration below).

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