Trailing Arm Bushes

A trailing arm runs lengthwise along the vehicle, anchored to the chassis at one end and carrying the axle or hub 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.

Trailing arm bushes carry that load, and they carry it constantly rather than occasionally, which is why they wear out faster than most people expect.

What Trailing Arm Bushes Take That Other Bushes Do Not

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

Every stop loads them in one direction and every take off loads them in the other, and on anything with real torque or real weight those loads are substantial. Rear trailing arm bushes can be finished on surprisingly low kilometres while the rest of the suspension still looks serviceable, which is exactly why the noise catches people by surprise.

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 useful on a standard vehicle. It is also the same softness that lets the axle move under load, and 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 Worn Trailing Arm Bushes Make the Rear End Steer Itself

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

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 vehicle is steering itself in small amounts you never asked for. It goes light and unsettled through a bumpy corner, wanders when loaded or towing, follows ruts and road camber rather than your steering input, and works through rear tyres faster than it should.

A wheel alignment reads correctly because the workshop measures the vehicle standing still, and standing still there is nothing wrong with it. The fault only exists while load is applied, which is why rear trailing arm bushes go unfound for years while people chase everything else.

Leave Trailing Arm Bushes Too Long and the Eye Goes Oval

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

A worn trailing arm bush does not simply 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 anything, because if it has gone oval, no bush will fix it and you need to know that before the vehicle is up on stands.

How Trailing Arm Suspension Differs From a Control Arm Setup

It helps to know what you are looking at, because trailing arm suspension behaves differently to the layouts most people picture.

A control arm runs across the vehicle and resists sideways load. A trailing arm runs along it and resists fore and aft load, which is why the two wear at different rates on the same vehicle and why the symptoms are not the same.

On a semi trailing arm design the arm sits at an angle between the two, taking some of each, and the bushes at the chassis end end up controlling both rear toe and camber as the suspension travels. That makes them unusually influential for their size, because a single worn bush is moving two alignment angles rather than one.

Live axle vehicles use trailing arms to locate the housing fore and aft while a panhard rod handles sideways location. On those, a worn rear trailing arm bush lets the axle move forward and back under power and braking rather than changing toe, which is what produces the wind up and release you feel as a shudder on take off.

Which Trailing Arm Bushing Position You Actually Need

Layouts differ between vehicles, 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 vehicle. Each arm also has a bush at both ends, and the chassis end and the axle 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 passenger car are completely different parts doing a related job.

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

Symptoms of Worn Trailing Arm Bushes

• 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 in the middle of a corner
• Wandering when the vehicle 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 rather than the first. By the time something clunks, the handling has been degrading for a while and the rear tyres have been paying for it.

Trailing Arm Bushes Replacement Cost and Where the Money Goes

The bushes themselves are inexpensive, and the labour to reach them is what determines the bill.

The arm has to come off the vehicle whichever route you take, and most positions need a press to get the old bushes out and the new ones in square. That work takes the same time whether you replace one bush or both ends of the arm, which is why doing one end now and the other in a year costs considerably more than doing both at once.

A wheel alignment afterward is worth having as well, since removing play changes the rear toe reading on an independent rear end.

When comparing quotes, the numbers that move the total are how many positions are being done, whether the arms have to come off the vehicle, and whether the workshop has quoted for the possibility of finding an oval eye once they are apart.

Pressing Trailing Arm Bushes In and Torque at Ride Height

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

Most positions need pressing, and a correct diameter press tool is what keeps the mounting eye intact. That matters more here than almost anywhere else, because the eye is the expensive part and there is no repairing one that has been damaged.

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 there is the step that matters more than all of the others, which is to torque with the vehicle on its wheels at ride height rather than 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 vehicle will pull under power and under brakes.

Find Trailing Arm Bushes for Your Vehicle

If the arm itself is bent or rusted, trailing arms are available as a complete replacement.

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 Nolathane component is backed by our warranty, a fitment guarantee and 60 day returns.