Trailing Arm Bushes

A trailing arm runs lengthwise along the car, anchored to the chassis at one end and carrying the hub or axle at the other. It holds the wheel in position fore and aft, which means everything you do with the throttle and the brake pedal passes through it.

The bushes at each end carry that load, and they carry it constantly rather than occasionally.

Every Launch and Every Stop Goes Through These

Most suspension bushes spend their lives managing vertical movement. Trailing arm bushes spend theirs absorbing the car trying to move its own axle.

Every stop loads them one way and every launch loads them the other, and on anything with real torque at the rear those loads are substantial. Rear trailing arm bushes can be worn out on surprisingly low kilometres while the rest of the suspension still looks healthy, which is exactly why people are surprised when the noise starts.

Factory rubber makes it worse because it is deliberately soft in the fore and aft direction. That compliance absorbs the shock of hitting a bump and keeps the cabin quiet, which is genuinely useful, but it is the same softness that lets the axle move under load. As the rubber ages and compresses, what was designed compliance turns into slop.

Polyurethane holds its shape under that loading, which is why the difference is most obvious under power and under brakes rather than over bumps.

Why the Back End Starts Steering Itself

This is the symptom nobody diagnoses correctly, because it does not feel like a bush.

The trailing arm holds the wheel in its fore and aft position, so anything that lets the arm move lets the wheel move with it. On an independent rear end that shows up as rear toe changing under load. On a live axle it shows up as the axle stepping slightly out of square, or winding up under power and releasing.

Either way the back of the car is steering itself. It goes light and unsettled through a bumpy corner, wanders when loaded or towing, follows ruts and road camber rather than your line, and works through rear tyres faster than it should.

An alignment reads correctly because the shop measures the car standing still, and standing still there is nothing wrong. The fault only exists while load is applied, which is why it goes unfound for years.

Leave Them and the Eye Goes Oval

There is a reason to act at the first symptom rather than the next service, and it is worth understanding before you put the job off.

A worn trailing arm bush does not just allow movement. Once there is enough play, the arm stops pivoting inside its mounting eye and starts working against it. The eye deforms slowly, a round hole becomes an oval one, and at that point a new bush has nothing round left to press into. It will not seat, it will not hold, and the arm itself needs replacing.

That is what turns a cheap job into an expensive one. Trailing arm bushes replacement cost is mostly labour even at the best of times, and the parts bill multiplies once you are buying arms rather than bushes.

Check the eye before you order. If it has gone oval, no bush will fix it.

Upper, Lower and Which End of the Arm

Layouts differ, so identifying the position matters when you order.

Some designs use a single trailing arm per side, others use an upper and a lower, and a lower trailing arm bushing is frequently a different size and hardness to the upper one on the same car. Each arm also has a bush at both ends, and the chassis end and the hub end are rarely interchangeable.

Add front or rear of the vehicle and you have the full description. A rear trailing arm bushing on a solid axle 4WD and the equivalent on an independent rear performance car are completely different parts doing a related job.

Bushes are matched to the housing rather than the vehicle alone, so if you are working on something modified, measuring the eye and searching by dimension will find a part when a vehicle lookup will not.

What You Notice, in the Order You Notice It

• A rear end that feels loose or unsettled under acceleration and braking
• Clunking or knocking from the rear on take up of drive, on gear changes, or when lifting off
• The back stepping sideways slightly over bumps mid corner
• Wandering when the car is loaded or towing
• Uneven or rapid rear tyre wear that no alignment explains
• A driveline vibration that shows up at a particular road speed on a raised vehicle
• Bushing material split, perished or squeezed out of the mounting eye
• A mounting eye worn oval, which means the arm needs replacing rather than rebushing
• Visible bending, cracking or heavy corrosion in the arm itself

The noise is usually the last of those to arrive, not the first. By the time something clunks, the handling has been degrading for a while.

Torque at Ride Height Decides Whether They Last

Support the axle or hub before releasing either end of the arm, and expect the rear to move once it is out.

Most positions need pressing, and a correct diameter press tool is what keeps the mounting eye intact. This matters more here than almost anywhere, because the eye is the expensive part.

Fit the crush tubes and sleeves supplied, since the tube carries clamping load from the bolt and a bush fitted without one gets crushed the moment the fastener is torqued.

Grease on assembly with a lubricant made for polyurethane. Silicone and PTFE based greases are correct, while ordinary lithium and petroleum based greases can degrade the material over time.

Then the important one. Torque with the car on its wheels at ride height, never at full droop. The bush is clamped between the arm and its mount, so whatever position you torque it in becomes its neutral position. Clamp it at droop and it spends its entire life twisted, binding at ride height and tearing itself apart from the first kilometre. More new trailing arm bushings are ruined by this than by anything else.

Do both sides, because one new bush against one worn one gives the rear axle two different rates of fore and aft movement and the car will pull under power and under brakes.

Finish with a wheel alignment, since removing play changes the rear toe reading.

Find Trailing Arm Bushes for Your Vehicle

Alignment bushes take things further when you need geometry correction too.

Select your vehicle to see the front and rear trailing arm bushes available for it, including upper and lower positions where the design uses both. Every Whiteline component is backed by our warranty, a fitment guarantee and 30 day returns.