Technical Bulletins | ATRO

Technical Bulletins

Technical Bulletins

Taper Pin Bushing Identification

 View as PDF

Technical Bulletin

HN Suspensions Evaluation / Replacement of Auxillary Spring and Shims

 View as PDF

Technical Bulletin

Once bolster springs are installed, the following evaluation should be performed. All measurements should be made on an unloaded truck.

  1. Measure height of auxiliary spring. Normal height of unloaded auxiliary spring is 3 3/8”. If the height of the unloaded auxiliary spring is 3” or less, the auxiliary spring should be replaced.
  2. Measure distance between saddle V bracket and bottom of auxiliary spring. Gap should not be larger than 3/8”.
  3. Add or remove shims above the auxiliary spring to achieve proper clearance.

Note: Failure to properly shim will force the load springs LP50-24000 to accept the full load and prevent the auxiliary spring LP50-24974 from engaging and carrying the significant portion of the load it is designed and required to carry. This produces additional stress on the load pads LP50-24000 and may cause premature failure and could void warranty.



TB001-012418 HN Suspensions

Engineering Change: EM75-61001, EM75-61001-HT Air Cooler Mount Kit

Technical Bulletin

EM75-61001 Air Cooler Mount Kit

To match the OE's kit, ATRO has added the following components to their original kit:

(2) Polyurethane Mount Bushings and

(2) Flat Washers

Now Contains:

  • (4) Polyurethane Mount Bushings
  • (4) Polyurethane Washers
  • (4) Bolts
  • (4) Flat Washers
  • (4) Locknuts
EM75-61001-HT Air Cooler Mount Kit (High Temperature)

To match the OE's kit, ATRO has added the following components to their original kit:

(2) Polyurethane Mount Bushings and

(2) Flat Washers

Now Contains:

  • (4) Polyurethane Mount Bushings (Hi Temp
  • (4) Polyurethane Washers (Hi Temp)
  • (4) Bolts
  • (4) Flat Washers
  • (4) Locknuts

Engineering Change TS34000 Crimped Design

 View as PDF

Technical Bulletin

TS34000 Crimped Design Torque Rod Busing

Crimped outer sleeve provides:
  • Increased support for polyurethane
  • Increased support and strength for urethane to metal bond
  • Easy installation due to radius on leading edge of bushing
New crimped design uses PT00-52600 installation & removal tool

PT00-52600 Installation & Removal Tool

The redesigned, crimped TS38000 Torque Rod Bushing, now uses this installation tool

EC002-040117 TS34000 Crimped Design

Torque Rods Critical for Concrete Mixers

 View as PDF

Technical Bulletin

Torque rods have multiple purposes in truck and trailer suspensions:

  • Restrain rotation of the axle housing during acceleration and braking
  • Locate the axle and maintain alignment
  • Control driveline angle
  • Absorb leaning and cornering forces

Concrete Mixer Impact:

In a concrete mixer application the drum rotates clockwise (as viewed from the rear) and this rotation shifts the load upwards and to the left side of the drum. This shift of load along with the high center of gravity built into the mixer design can contribute to rollovers when the truck is making right turns. Loose or worn torque rod bushings will reduce the torque rod’s ability to absorb the cornering forces and can contribute to the rollover possibility. For this reason it is very important to routinely check the torque rod bushings for movement. This can be done by prying against the bushing or simply rocking the truck forward and backward while observing the bushings. Any movement greater than 1/8” should be addressed by replacing or re-bushing the torque rod.

Worn Torque Rods:

  • Contribute to mixer roll-over
  • Affect driveline angles & U-Joint wear
  • Contribute to misalignment & tire wear
  • Contribute to ring & pinion failure
  • Can cause leaking transmission & differential seals

  • Replacement Bushings
  • Two-piece weldable torque rods
  • Complete OEM replacement torque rods including Terex Advance Mixer Rods
 Torque Rod Finder

ATRO Torque Rod Bushings:

  • Polyurethane material is more durable than rubber
  • Polyurethane material is impervious to chemical attack (includes acidic cleaning solvents)
  • Feature rotating pins that automatically “zero out” to ride height and allow easier installation
  • Rotating pins allow for multiple OEM rod replacements with one rod

TB001-021715 Torque Rods Critical for Concrete Mixers

Determining Correct Replacement Torque Rods

 View as PDF

Technical Bulletin

Primary Torque Rod Designs (ranked by popularity):

  1. Straddle/Straddle: mounting bolt type on both ends
  2. Straddle/Taper: one end mounting bolt type, one end tapered pin end
  3. Taper/Taper: tapered pin on both ends
 Torque Rod Finder

ATRO Torque Rod Solutions:

  1. Two-Piece Weldable Torque Rods: two ends welded to length
  2. Direct Replacement Torque Rods: complete rod

If a customer prefers a direct replacement torque rod, the only tool needed to identify the correct replacement rod is a tape measure.

Information to get from customer:

  1. Torque Rod Design (i.e., taper/taper)
  2. Center to Center Length

You can verify the accuracy of the chart by checking against the listed OEM cross reference number.

ATRO torque rod ends feature a polyurethane material with free rotating pins.

For the next repair cycle, ATRO offers bushings for these replacement rods.

In many cases, the OEM bushings can be replaced with an ATRO bushing with its unique features.

TB001-070714 Determining Correct Replacement Torque Rods

Spring Eye Bushings

 View as PDF

Technical Bulletin

Relative to the following ATRO Parts:

When switching from threaded, metal style pin and bushing to ATRO’s Polyurethane Spring Eye Bushing, use the conversion chart below, find your corresponding bushing and pin number and pick the ATRO part number in the box where they intersect. This is a total replacement for both the pin and bushing.

The ATRO parts listed in the conversion chart below are designed as a replacement for the threaded bushing style spring pins. The ATRO parts are a one piece design.

ATRO Features and Benefits:

  • Simplify by replacing both the pin and bushing
  • Self lubricating quality, meaning no more grease
  • ATRO’s polyurethane material is impervious to oil, grease, brine, cleaning solvents, hydraulic fluids and diesel fuel
  • Premium polyurethane is formulated for superior performance

Conversion Chart: Threaded Spring Pin Bushing to Polyurethane

Bushing Part Number
Conventional & Cab Over Trucks 4" Springs
 Paccar B13-1000
Dayton Parts TB77
Automann MTB178
Paccar B13-1002
Dayton Parts TB81
Automann MTB186
Pin Part Number  
Paccar B65-1002
Dayton Parts 327-537
Automann M5448
Paccar B65-1008
Dayton Parts 327-540
Automann M5449
Paccar B65-6008
Dayton Parts 327-544
Automann M5447

ATRO Installation Tools:

TB001-072017 Spring Eye Bushings

KT50-2500 Haulmaax Suspension Kit

 View as PDF

Discontinued Part Number

Technical Bulletin

ATRO has discontinued the KT50-25000 Haulmaax® Suspension Kit. In its place you should order the KT50-25002 or the KT50-25003. (The KT50-25003 kit includes a set of 4 wear plates.)

The difference between the KT50-25000 and the KT50-25002 is the Auxiliary Load Spring has been replaced with the NEW Progressive Load Spring.

In 2014, Hendrickson Truck Commercial Vehicle Systems introduced the Progressive Load Spring for Haulmaax® vocational rear suspension system. The NEW Progressive Load Spring works together with the bolster springs.

The PLS replaces the auxiliary load spring. It provides improved ride quality and stability.

As payload increases, the PLS further engages and functions together with the rubber bolster springs to provide additional stability. The PLS’s constant engagement also eliminates the need for shim adjustments, resulting in reduced maintenance and lower cost.


  • The LP50-24974 Auxiliary Load Spring with Hardware is still available for purchase.
  • It is also available in the LP50-24746 Kit for Weight Bias Vehicles.

TB002-032416 KT50-2500 Haulmaax Suspension Kit

Intraax/Vantraax Tri-Functional Bushing

 View as PDF

Why Choose Premium ATRO Products

Technical Bulletin

ATRO has two bushing choices to replace the OEM #S-24691 Intraax/Vantraax trailer suspension bushing

Both ATRO products offerthese benefits:

  • ATRO's polyurethane is impervious to chemical attack unlike rubber bushings
    • Oil & Greese
    • Calcium Chlordie (Winter Salt Melt)
    • Citric Acid & Acid Based Cleaners
    • Ethylene Glycol
    • Gas, Kerosene & Diesel Oil
    • Many additional contaminants
  • ATRO's polythurethane is 2-5 times stronger than rubber!
Results: ATRO Intraax Bushings last longer and are backed by the industry's best warranty.
Tri-Funcitonal Design Bushing PB50-36000 & PB50-36001
  • The bushing has voids, similar to the OEM bushing.
  • It's outside diameter (OD 5 7/8" is similar to the rubber bushing's 6" OD.
  • ATRO's bushing and the rubber bushing are compressed into the 5 1/2" ID beam hole.
  • The ATRO offers the PT50-59307 installation tool, which can be used to install both ATRO's bushing and the rubber OEM bushing.
  • w/ Hex Head Bolt
  • w/ Shear Bolt
ATRO Part NumberEasy InstallVoidsInner Pin RotationBolt typeTorque
PB50-36000NoYesNoHex Head500-550 ft. lb.
PB50-36001NoYesNoShear BoltHead snaps off at proper torque

TB002-071018 Intraax/Vantraax Tri-Functional Bushing

TR59-41474 Steel Torque Rod

 View as PDF

Technical Bulletin


  • Kenworth K195-474
  • Kenworth K195-472 (no bushings)


  • Airglide 200, 400, 460

With High Articulating Straddle Pin Bushing TS59-22400

The Kenworth aluminum OEM rods are mounted in a V formation with the torque rod straddle bushing mounting pins facing up and down. When the axles articulate the pin is forced to move sideways (conical movement) in the bushing. This movement is not designed into the OEM rubber bushing or the ATRO TS38000. This forced movement will rapidly wear the torque rod bushing. In severe cases, it can contribute to breaking the aluminum torque rod. ATRO designed a torque rod bushing with a higher allowable side to side, conical movement in the bushing. This bushing uses an oval pin configuration and articulation voids designed into the polyurethane. This design allows the bushing to move 12° in both directions, 24° total movement. This greatly extends the bushing life and relieves the stress on the torque rod.

The ATRO TS59-22400 high articulating bushing is a direct replacement for the OEM rubber bushing and can be pressed into the aluminum OEM torque rod.

The ATRO TR59-41474 replacement torque rod is a steel replacement rod with the two high articulating bushings included and directly replaces the OEM aluminum torque rod.


Torque Rod Bushing, High Articulation


  • Kenworth 227720, 836940, 839310


For additional information in regards to the TR59-41474 and TS59-22400, please see ATRO’s Product Spotlight PS005-022217

TB002-092017 TR59-41474 Steel Torque Rod

Mack Pads Indentification

 View as PDF

Technical Bulletin

TB003-072314 Mack Pads Indentification

LP50-24179 Haulmaax® Bolster Spring Kit

 View as PDF

Technical Bulletin

ATRO LP50-24179 Haulmaax Bolster Spring Kit
LP50-24179 — Bolster Spring Kit

ATRO bolster springs are designed to meet the OE Load Curve. ATRO’s Polyurethane is stronger not harder than the OE rubber and is designed to improve suspension performance.


  • Improved durability, enhanced load handling capabilities and increased stability by removing grooves to provide more load bearing area
  • Reduced ride height by 3/8” to ensure overload spring can engage


  • Do not use both old and new bolster springs on the same truck
  • Do not mix rubber bolster springs with any ATRO bolster springs on the same truck
  • Adjust Auxiliary Springs to within ¼”- ½” of shim plates when truck is unloaded. Auxiliary Springs should be contacting the shim plates when truck is fully loaded.
  • Any excessively worn Auxiliary Springs must be replaced. ATRO’s new progressive load spring LP50-24778 is recommended. The original auxiliary spring LP50-24947 is also available.

TCB001-022312 LP50-24179 Haulmaax Bolster Spring Kit

SW59-29000 & SW59-29001 Redesigned Kenworth Sway Bar Kits

 View as PDF

Technical Bulletin

The listed guidelines must be followed concerning the ATRO Kenworth Sway Bar SW59-29000 and SW59-29001 Sway Bar Kits:

  • Kits are only intended for retrofitting the Kenworth Airglide 200 suspension to the Kenworth Airglide 380/400 suspension and/or for rebuilding the Kenworth Airglide 400/460/690 suspension for all applications
  • Use only ATRO polyurethane bushings in conjunction with ATRO sway bars (bushings are supplied with each sway bar kit)
  • Shaft collar (SW59-29599 optional) & thrush bushing (SW59-29454 optional) not required on this design.
  • Ensure all torque rods and torque rod bushings are in good working condition
  • Maintain proper ride height, as specified by the OEM application
  • Follow industry best practice for install, repair and safety
  • Do not re-use old bushings or hardware
  • Do not mix ATRO sway bars with non-parabolic designed sway bars or other manufacturer’s sway bars
  • It is recommended that procedures from a factory service manual be followed for removal, replacement and proper torque specifications

TG031309 SW59-29000 & SW59-29001 Redesigned Kenworth Sway Bar Kits

PB75-29101 & PB75-29674 Peterbilt Air Leaf Bushing Kits

 View as PDF

Technical Bulletin

  1. Insert the inner polyurethane sleeves into each end of the eye casting. Insert the steel spacer tube and seat the bushings as far into the casting as is possible before the spacer tube tightens up. Remove the spacer tube.
  2. NOTE: Please be aware that the inner polyurethane sleeves in our kits are tapered and must be inserted into the eye casting small end first. (The OE rubber parts are straight sided and can be installed from either end.)
  3. Insert the eye casting into the hanger and align the eye casting eye with hanger’s eye. (This may be a tight fit.)
  4. Insert the spacer tube through the hanger eye and into the inner polyurethane bushings.
  5. nstall the hard polyurethane washers into both ends of the hanger (stepped side inwards). You may have to tap them down to seat them.
  6. Insert a compression washer on both ends with counter-bored side facing outwards.
  7. Run bolt through entire assembly from the outboard side. (If end of bolt does not protrude sufficiently to start nut either reseat the hard polyurethane washers or use a longer bolt and nut to reseat the whole assembly.)
  8. Install nut and torque to manufacturer’s specification. (Do not reuse old bolts.)

TG103009 PB75-29101 PB75-29674 Peterbilt Air Leaf Bushing Kits

TR59-41474 Torque Rod Kenworth AirGlide

 View as PDF

Technical Bulletin


Torque Rod


Kenworth#: K195-474 (Aluminum)


Kenworth Airglide 200/400/460/690

The TR59-41474 Torque Rod was designed specifically for the Kenworth Airglide suspension and replaces the original aluminum rod with a stronger, more durable alternative. The Kenworth Airglide suspension design combines the transverse and tracking torque rods into a dual rod, V configuration with the torque rods mounted vertically. This design requires an extreme amount conical motion from the bushings due to the torque rods being mounted vertically instead of the more familiar horizontal arrangement. This mounting configuration places much more bending stress on the rod. To handle this additional stress the improved ATRO rod features forged steel rod eyes and a heavy-walled steel shaft. Additional conical movement was also added by equipping our rods for this application with the new ATRO TS59-22400 High Articulation Bushing. While this bushing does not have the trademark ATRO rotating feature which has made our standard torque rod bushings so popular in the heavy duty trucking industry, it does utilize articulation voids and a modified pin to provide the extra vertical motion required by this very demanding application. This bushing is the only bushing approved by ATRO for use in Kenworth Airglide 200/400/460/690 aluminum rods (K195-474 and K195-472).

TIB TR59-41474 Torque Rod Kenworth AirGlide

Suspension Inspection Maintenance

 View as PDF

Technical Bulletin

Today’s heavy duty suspensions are called on to carry loads for more miles and under harsher conditions than ever before. Keeping an eye on these suspensions help keep trucks on the road and stress free. Air Spring and Leaf Spring suspensions each have critical wear points that need to be reviewed regularly.

Common Air Suspensions: Freightliner FASII, Kenworth AirGlide 400, Peterbilt Air Leaf, Peterbilt Air Trac


Leaking air or restricted air flow

  • If both sides are flat, there may be a leak between the air brake system and the suspension air system
  • If flat on one side, there may be a leak between the height control valve and the air spring

Automatic height control valve

  • Test it: disconnect linkage and move actuating arm up and down to see if air bag inflates/deflate.


  • Place pry bar between trailing arm and hanger and check for movement - abnormal tire wear is a good indicator of bushing wear

Shocks - should be warm to the touch after vehicle operation

  • If cold, the shock is not functioning properly and should be replaced
  • If shock can be easily compressed after removal, shock should be replaced
  • Check for shock bushing wear

Under-inflation - slight positive pressure maintains shape of air bag and prevents folding/pinching

Causes of Air Spring failure:

  • Overextension
  • Abrasion
  • Contamination
  • uspension Misalignment
  • Road Hazards
  • Fatigue/Old Age


TT001-050118 Suspension Inspection Maintenance