Your truck pulls slightly to one side under hard braking, even though the alignment was done recently and the brakes seem balanced. Or you hear a clunk from the rear when you accelerate from a stop, deeper and more directional than a simple bushing knock. These symptoms often point to the torque rods: the suspension links that control axle position under braking and acceleration loads.
At Ressorts Laval, torque rod inspection is a standard part of our rear suspension check. They are one of the most commonly overlooked components on high-mileage heavy trucks, and one of the most cost-effective to maintain.
What do torque rods and radius rods do?
On a leaf spring suspension, the springs do two jobs: they support the vehicle weight and they keep the axle in position longitudinally. But on many rear suspension designs, particularly on trucks with air suspension, Hendrickson walking beam suspension or certain tandem configurations, the springs are not designed to handle longitudinal forces alone.
That is where torque rods come in. Also called radius rods or track rods depending on the design, they are solid or tubular steel links that connect the axle housing to the truck frame. They do not carry vehicle weight. Instead, they:
- Prevent the axle from moving forward under hard braking (reaction torque)
- Prevent the axle from moving rearward under hard acceleration (drive torque)
- Keep the axle square to the truck centerline on suspension with angled or offset mounts
Each torque rod has a bushing at each end: a rubber or polyurethane bushing that allows slight rotational movement while absorbing vibration. These bushings are the wear point.
Signs of worn torque rod bushings
Clunk on acceleration from a stop
The most characteristic symptom. When you pull away from a red light, the drive torque pushes the axle rearward. If the torque rod bushings are worn and have developed play, the axle moves that small amount and then hits the end of the play with a clunk. You hear and feel it through the cab floor.
Clunk on hard braking
The same principle in reverse. Under braking, the axle tries to move forward. Worn bushings allow that movement and produce a clunk as the rod takes up the slack. Some drivers describe it as feeling like the axle is “shifting” under hard stops.
Truck pulling to one side under braking
If one torque rod bushing is significantly more worn than its counterpart on the other side, the two rear axle positions are not symmetrical under load. Under hard braking, the truck pulls toward the side with the more worn bushing.
Uneven rear tire wear across the axle
A torque rod that has lost its bushing integrity allows the axle to sit slightly skewed relative to the truck centerline. That changes the effective toe on the rear axle and causes uneven tire wear that no wheel alignment can correct as long as the bushing is worn.
⚠️ Warning
A truck that pulls under braking because of worn torque rods is a safety issue, not just a maintenance item. Under emergency braking with a full load, that pull becomes more pronounced. Do not delay inspection if you notice this symptom.
Adjustable vs. fixed-length torque rods
Most torque rods are fixed-length and simply replaced when worn. However, some suspension systems use adjustable torque rods: rods with a threaded center section that allows the rod length to be changed. This is particularly useful on tandem setups where individual axle position needs to be fine-tuned for parallelism.
💡 If your truck has adjustable torque rods, axle position adjustment is part of a proper laser alignment procedure on the rear axles. Make sure your alignment shop checks this. Not all do.
What does torque rod repair cost?
| Repair | Price range |
|---|---|
| Torque rod bushing replacement (per rod) | $150 to $350 |
| Full torque rod replacement | $300 to $700 per rod |
| All torque rods on one tandem axle set | $600 to $1,800 |
| Axle alignment after torque rod adjustment | + $200 to $350 |
Replacing torque rod bushings in pairs is standard practice. If the bushings on one rod are worn, the ones on the opposite rod almost certainly are too. Replacing both eliminates the clunk and restores symmetrical braking behavior.
Frequently asked questions
How long do torque rod bushings last?
On a highway truck, 300,000 to 500,000 km is typical. On a construction truck or a truck that does a lot of urban stop-and-go with heavy loads, 150,000 to 250,000 km is more realistic. The high torque cycles of frequent stop-and-go in a loaded truck wear them faster.
Can you just replace the bushing, or do you need to replace the whole rod?
In most cases, just the bushing. We press out the worn bushing and press in a new one. We only replace the rod itself if the housing is damaged or if the rod body is cracked or bent.
Is the clunk on acceleration always torque rods?
No. A clunk on acceleration can also come from worn U-bolts, loose leaf spring center bolts, worn equalizer pivot bushings or even a worn drive shaft U-joint. Torque rods are a common cause, but the diagnosis needs to confirm it. That is what the lift inspection is for.
Do all heavy trucks have torque rods?
No. Trucks with full leaf spring suspension (no air suspension, no walking beam) often use the springs themselves to locate the axle and do not have torque rods. They are most common on air suspension and Hendrickson walking beam suspension configurations.
Clunk on acceleration? Pulling under braking?
We inspect torque rods, equalizer beams and all rear suspension components. Ressorts Laval, suspension specialists in Laval since 1971.
Call us at 450-661-5157.