TECHNICAL
Procedure

TRI-FUNCTIONAL® BUSHINGS


SUBJECT: Bushing Tube Spacer
Inspection / Replacement Procedure
LIT NO: L750 
DATE: November 2015
REVISION: C

Frame bracket

Alignment collar

Bushing tube

Beam assembly

TRI-FUNCTIONAL®
Bushing
(wide shown)

Pivot bolt hardware

Bushing tube spacers

Bushing inner metal

TABLE OF CONTENTS
Inspecting Bushing Tube Spacers............................................................................................................2
Evaluating Bushing Position Within The Bushing Tube..............................................................................4
If Bushing Tube Spacer is Worn Through.................................................................................................4
Evaluating Frame Bracket Wear..........................................................................................................5
Evaluating Bushing Tube Wear...........................................................................................................5
Repair Recommendations..................................................................................................................6
Bushing Tube Edge Dressing..............................................................................................................7
Installing The New Bushing....................................................................................................................7
Replacement Bushing Tube Spacer, Wide Bushing................................................................................8

Bushing Tube Spacer Inspection / Replacement Procedure
This document, along with the following Hendrickson publications, comprise the complete set of bushing,
bushing tube and bushing tube spacer inspection, evaluation and replacement information:
L1071 Pivot Bushing Inspection/Replacement Information
L1073 Fixed Suspension Installation Information and Requirements
L1074 Slider Suspension Installation Information and Requirements
L578 Preventive Maintenance Guide
These Hendrickson publications, and any others that may be referenced on the following pages, are available as
free downloads from www.Hendrickson-intl.com/TrailerLit. If more information is required, contact Hendrickson
Trailer Technical Services: in the United States and Canada at 866-RIDEAIR (743-3247) or email
HTTS@Hendrickson-intl.com.
The bushing tube (shown on front cover) evaluation information in this document applies to both wide and
narrow bushing types (Table 1).
BUSHING
TYPE

BUSHING
TUBE WIDTH

TRI-FUNCTIONAL® II Bushing (TF II)

Wide

6"

TRI-FUNCTIONAL III Bushing (TF III)

Narrow

31/8"

DESCRIPTION

APPLICABLE SUSPENSION TYPES
INTRAAX®, VANTRAAX® and HT™ Series
INTRAAX, VANTRAAX and ULTRAA-K®

Table 1: Bushing types

INSPECTING BUSHING TUBE SPACERS
Frame bracket

Evaluate the
condition of
these bushing
tube spacers

Bottom view of pivot connection (See details on page 8)
Forward

Figure 1: Bushing tube spacer location

2

L750 C

Bushing Tube Spacer Inspection / Replacement Procedure
Periodic inspections are an important part of an air suspension maintenance routine. Of particular importance
are the bushing tube spacers, which are located inside the frame brackets on each side of the TRI‑FUNCTIONAL®
Bushing (front cover and Figure 1). For inspection intervals, refer to Hendrickson literature number L578
Preventive Maintenance Guide. An evaluation should include all bushing tube spacers on the trailer.
NORMAL

Normal
bushing
tube spacer

Normal bushing tube spacer in serviceable
condition.

“CUPPED” — ALSO NORMAL

“Cupped”
bushing
tube spacer

“WORN-THROUGH” — ABNORMAL

“Worn-through”
bushing tube
spacer

An example of a “cupped” bushing tube
spacer. Friction-generated heat causes
the spacer to “form” or “cup” around the
bushing and bushing tube. This is normal
and serviceable as long as the bushing
tube spacer remains intact and does not
become cut or worn-through.
Figure 2: Bushing tube spacer examples

Examples of “worn-through” bushing tube
spacers. The spacer on the right is an
example of extreme wear. Its circumference
has been completely trimmed by the
bushing tube. The spacer is not in
serviceable condition.

Visually verify that the bushing tube spacers are intact and are not missing, cut, worn-through or otherwise
deteriorated. Due to the pivoting motion inherent with this connection, some bushing tube spacer wear is
expected (Figure 2). Bushing tube spacer “cupping”, where the bushing tube spacer forms around the bushing
tube and resembles a shallow dish, is also normal. If you see these conditions, no further inspection is required
at this time. The bushing tube spacers are in serviceable condition.
However, a bushing tube spacer that is completely missing, has been cut or worn through is considered
abnormal. If these conditions exist, a closer, more detailed inspection is required to prevent serious or
costly problems and to prolong the life of the suspension.

L750 C

3

Bushing Tube Spacer Inspection / Replacement Procedure

EVALUATING BUSHING POSITION WITHIN THE BUSHING TUBE
NOTE: This procedure is not required if replacing the beam (HT™ Series suspensions) or HALFTRAAX™.
For evaluation purposes, the TRI‑FUNCTIONAL® Bushing is considered either centered or off-center with respect
to the bushing tube (Figure 3). The TRI‑FUNCTIONAL Bushing is considered off-center when a portion of the
rubber extends outside of the bushing tube on one side and not on the other.
Centered

Centered

Centered

Off-center

Off-center

Figure 3: Typical examples of bushing position relative to the bushing tube (not representative of every possible case).

The key to identifying an off-center bushing is the bushing tube spacers. If the bushing tube spacers are in
serviceable condition (not missing, cut, worn-through or otherwise deteriorated), the bushing cannot be offcenter (Figure 3).
If the bushing is off-center, but the bushing tube width is acceptable, replace the bushing. Refer to Hendrickson
literature number L427 Bushing Replacement Procedure for complete bushing replacement instructions.

IF BUSHING TUBE SPACER IS WORN THROUGH

If a missing, cut or otherwise worn through bushing tube spacer is discovered, the suspension pivot connection
must be disassembled and the beam assembly lowered to check for potential beam and/or frame bracket wear
(Figure 4). Refer to Hendrickson literature number L427 Bushing Replacement Procedure for complete pivot
connection disassembly instructions.
CAUTION: Chock trailer wheels on the down axle, if available, and apply the trailer parking brakes so
that it cannot move during disassembly. Follow local shop safety practices.
Frame bracket
Inspect the position of the
TRI-FUNCTIONAL Bushing
within the bushing tube
Inspect the entire edge
surface on both sides of
the bushing tube for wear

Bushing tube

Inspect both inner
surfaces for wear
Beam assembly

Figure 4: Pivot connection component inspection

With the beam assembly lowered (Figure 4), inspect inner surfaces of the frame bracket and edges of the
bushing tube for wear. Also inspect the position of the TRI‑FUNCTIONAL Bushing within the bushing tube.
The condition of these three areas will dictate the repair requirements or the necessity to replace any parts as
instructed in Table 2 on page 6.
4

L750 C

Bushing Tube Spacer Inspection / Replacement Procedure
EVALUATING FRAME BRACKET WEAR

With the beam assembly lowered (Figure 4), inspect the inner surfaces of the frame bracket. Some wear
(polished metal) on the inner surface of the frame bracket is considered normal due to the pivoting motion
inherent with this connection. Gouges or grooves worn into the frame bracket are abnormal. If any gouges,
grooves or missing metal is found, the frame bracket must be replaced. For complete frame bracket replacement
instructions, refer to applicable Hendrickson literature listed at the top of page 2.
After the frame bracket evaluation is complete. Continue with EVALUATING BUSHING TUBE WEAR.

EVALUATING BUSHING TUBE WEAR

Some wear (polished metal) on the edge of the bushing tube is considered normal (Figure 5) due to the pivoting
motion inherent with this connection. Missing metal where the bushing tube’s radius edge has been worn away
is considered abnormal. If this type of wear is present, determine how much wear has occurred.

Radius intact

Radius worn away

Normal tube edge

Abnormal (worn) tube edge
Figure 5: Bushing tube edge wear (wide bushing)

The amount of bushing tube wear can be determined by measuring the width of the worn bushing tube
(Figure 6) and subtracting this measured dimension from the new tube width.
BUSHING
TYPE

NEW TUBE
WIDTH

Wide

A=6"

Narrow

A=31/8"

A

See Table 2 on page 6 for
specifications

Figure 6: Bushing tube width

For example (wide bushing):
Suppose the inspection reveals extensive bushing tube wear and the bushing tube measures 515/16 inches.
Subtracting 515/16 from 6 reveals the amount of bushing tube material that has worn away, in this case 1/16 of an
inch.
6" - 515/16" = 1/16"
Refer to the REPAIR RECOMMENDATIONS for repair procedures based on bushing tube width.

L750 C

5

Bushing Tube Spacer Inspection / Replacement Procedure
REPAIR RECOMMENDATIONS

Once each pivot connection component has been evaluated, and if bushing tube spacers are missing, cut
or otherwise worn through; use the following table to determine the correct repair action. DO NOT add more
bushing tube spacers than what is recommended in the table. A slight degree of freedom is required by the
TRI‑FUNCTIONAL® Bushing within the frame bracket to flex, elongate and otherwise absorb forces generated by
braking, accelerating, turning and irregular road surfaces.
NOTICE: If more bushing tube spacers than what is recommended are added, the TRI‑FUNCTIONAL®
Bushing will not have enough room within the frame bracket to function properly and severe
damage to the suspension could result.
IF THE BUSHING TUBE MEASURES:

AND THE
BUSHING IS:

Wide TF II

Narrow TF III

57/8 to 6"

31/8 ±1/32"
(No wear on the
bushing tube) 6

(No wear on the
bushing tube)
5¾" TO 57/8"
(Wear of 1/8" to ¼"
on the bushing tube)

N/A

Less than 5¾"
(More than ¼"
wear on the
bushing tube, Worn
into the weld) 6

Less than 33/32"
(Worn into the
weld) 6

1
2
3
4

5
6

Centered 1
Off-centered 2, 3

THEN:
Replace both bushing tube spacers and realign the axle. 2, 5
1. Install new bushing. Refer to L427 Bushing Replacement
Procedure for complete instructions.
2. Replace both bushing tube spacers and realign the axle.

N/A

1. Remove existing bushing and dress the radius on the bushing
tube edge according to the instructions in this document.
2. Install new bushing. 4 Refer to L427 Bushing Replacement
Procedure for complete instructions.
3. Replace both bushing tube spacers and realign the axle.

N/A

1. Replace the HALFTRAAX™ or the beam assembly. Refer to
L533 HALFTRAAX™ Axle and Beam Removal/Replacement
Procedure for complete HALFTRAAX replacement instructions for
complete beam replacement instructions.
2. Replace both bushing tube spacers and realign the axle.

Refer to the paragraph titled Figure 3 on page 4 for centered/off-center bushing definitions.
Refer to Hendrickson literature number L579 Alignment Procedure for complete axle alignment instructions.
DO NOT attempt to center an off-center bushing (Figure 3). Remove the off-centered bushing and install a new one.
Wide bushing only: Install the new bushing from the worn side of the bushing tube. Refer to the paragraph titled REPLACEMENT BUSHING TUBE
SPACER, WIDE BUSHING on page 8 for complete details.
Refer to the paragraph titled REPLACEMENT BUSHING TUBE SPACER, WIDE BUSHING on page 8 for installation details.
Any bushing tube wear into the weld is not acceptable. In this case, the axle/beam weldment (HALFTRAAX) will need to be replaced.

Table 2: Bushing tube measurement evaluation

6

L750 C

Bushing Tube Spacer Inspection / Replacement Procedure
BUSHING TUBE EDGE DRESSING

As described in Table 2, it is acceptable to reuse the bushing tube if within the specifications listed in the table.
However, the bushing tube edge must be dressed before the new bushing is installed. If not properly dressed,
bushing tube and frame bracket components will wear more rapidly than normal.
Before attempting to install a new bushing, the worn bushing tube edge must be dressed. Use a grinder to
re‑establish a radius on the edge of the bushing tube as shown in Figure 7 and defined in Table 2.
Section AA before grinding edges

Section AA after grinding
/8" minimum, 3/16" maximum ID radius

1

“Hook” develops
due to wear
/16" minimum, 1/8" maximum OD radius

1

NOTE: ID radius must be smooth for
bushing installation, ID & OD
radius must be smooth for bushing
tube spacer.
Figure 7: Repairing bushing tube edge

When the bushing tube wears, a slight “hook” or “tooth” of metal may develop on both inside and outside
diameters of the tube (Figure 7). As the vehicle turns, the unique design of the TRI‑FUNCTIONAL® Bushing allows
it to elongate sightly to absorb the forces associated with road surface, load, etc. When the turn is complete
and those particular forces are no longer present, the TRI‑FUNCTIONAL Bushing returns to its original position.
If the “hook” or “tooth” on the bushing tube is not removed, it can “bite” into the rubber TRI‑FUNCTIONAL
Bushing when elongated and hold or prevent it from returning to its original position, which is unacceptable.
As this is repeated, the TRI‑FUNCTIONAL Bushing can eventually be pulled out of the bushing tube. The rubber
TRI‑FUNCTIONAL Bushing may also become damaged by these irregular edges.

INSTALLING THE NEW BUSHING

The new bushing must be installed from the worn side of the bushing tube. If improperly installed, components
will wear more rapidly than normal. Refer to Hendrickson literature number L427 Bushing Replacement
Procedure for complete bushing tool and bushing replacement details.
CAUTION: After reassembly, remove wheel chocks and release the trailer parking brakes before moving
the trailer.

L750 C

7

REPLACEMENT BUSHING TUBE SPACER, WIDE BUSHING

When installing the replacement bushing tube spacers (part number S-21099), ensure the recessed side of
each spacer faces the bushing tube as shown in Figure 8.
NOTE: This information does not apply to narrow bushing tube spacers. Refer to trailer parts catalogs;
available online at www.hendrickson-intl.com/parts.

NOTE: Machined recess
on S-21099 spacer
must face toward
the exposed surface
of the bushing.

REPLACES

Replacement aftermarket spacer S-21099
(thick)

AND

Original flat spacer (thin)

Cap style spacer

Previously available or current spacers

Figure 8: Bushing tube spacer orientation (wide bushing)

For additional technical support, contact Hendrickson Trailer Technical Services, in the United States and
Canada at 866-RIDEAIR (743-3247) or email [email protected].

Call Hendrickson at 866.RIDEAIR (743.3247) for additional information.
TRAILER COMMERCIAL VEHICLE SYSTEMS
2070 Industrial Place SE
Canton, OH 44707-2641 USA
866.RIDEAIR (743.3247)
330.489.0045 • Fax 800.696.4416

www.hendrickson-intl.com
L750 Rev C 11-15 ECN 24337

Rev B 09-07 ECN 16034

Rev A 08-05

Hendrickson Canada
250 Chrysler Drive, Unit #3
Brampton, ON Canada L6S 6B6
800.668.5360
905.789.1030 • Fax 905.789.1033

Hendrickson Mexicana
Circuito El Marqués Sur #29
Parque Industrial El Marqués
Pob. El Colorado, Municipio El Marqués,
Querétaro, México C.P. 76246
+52 (442) 296.3600 • Fax +52 (442) 296.3601

01-01

Information contained in this literature was accurate at the time of publication. Product changes may have been made after the copyright date that are not reflected.

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