Body Mount Bushings

Every suspension component is bolted to something, and on most vehicles that something is bolted to something else through rubber.

Body mount bushings are the last joint in that chain, and when they soften, everything the suspension does arrives at a body that is already moving.

What Body Mount Bushings Do

On a body on frame vehicle the body is a separate structure bolted to a ladder chassis, and it sits on a set of rubber mounts at each attachment point.

Those mounts are doing two separate jobs at once. They isolate the cabin from the noise, vibration and flex the chassis experiences, and they allow a small amount of relative movement between the two structures so neither has to carry the other's twisting loads.

A vehicle typically runs somewhere between eight and a dozen of them, spread along both chassis rails.

The compromise involved should be familiar by now. Softer rubber gives a quieter, smoother cabin and allows the body to move on the frame. Firmer holds the two together and lets more through.

Subframe Bushings on Unibody Vehicles

The same principle appears on cars with no separate chassis.

A unibody vehicle carries its suspension on front and rear subframes, and those subframes bolt to the body through bushings rather than directly.

Everything the suspension does passes through those mounting points. Cornering loads, braking loads and the torque reaction from the differential on a rear drive car all reach the body through four bushings.

Rear subframe bushings are the ones that matter most on a performance car. Under power the differential tries to rotate, and a soft subframe bushing lets the whole assembly move before the body resists it.

That movement shows up as wheel hop, delayed power delivery and a rear end that feels less connected than the suspension parts suggest it should be.

What Worn Body Mounts Feel Like

• Creaking or groaning from the body over driveways and speed humps
• Doors, hood or tailgate alignment changing or becoming harder to close
• A rattle or shudder through the cabin on rough surfaces
• The body feeling like it moves separately from the chassis in corners
• Wheel hop under acceleration on a rear drive car with worn subframe bushings
• Visible gaps or sagging at the mounting points
• Rubber that has cracked, collapsed or squeezed out past the washer
• A vehicle that sits lower than it should with no suspension fault

Door and panel alignment changing is the giveaway on a body on frame vehicle. The body is sitting lower on collapsed mounts, which moves every aperture slightly.

Why They Collapse

Rubber under constant compression does not last indefinitely, and these carry the weight of the body permanently.

Heat accelerates that whole process a great deal. Mounts near the exhaust or the engine bay degrade faster than those further back, which is why a vehicle often has a few that are badly gone and others that look acceptable.

Water sits in the mounting cups and corrodes the sleeves and bolts, which is what turns a straightforward job into a difficult one.

Age and load take care of the rest. A vehicle carrying weight, towing or working on rough surfaces compresses its mounts harder and more often.

What Firmer Body Mounts Change

Replacing collapsed rubber with polyurethane does more than restore the original position.

The body and chassis start working as one structure rather than two connected loosely. Chassis flex that used to be absorbed in the mounts now has to be carried by both, which makes the whole vehicle feel stiffer and more deliberate.

Steering response improves on a body on frame vehicle, since the steering box or rack is mounted to the chassis and the driver is sitting in the body. Less movement between the two means less lost motion between input and response.

On a unibody car with firm subframe bushings, the suspension geometry stays where it was designed rather than shifting as the subframe moves under load.

The trade is roughly what you would expect. More road noise, more vibration and more of the structure's behavior reaching the cabin, which is the exchange for control.

Body Mount Bushing Kits

These are sold as complete kits for a reason.

Replacing one or two mounts while leaving the rest means the body is held firmly at some points and loosely at others, which concentrates load at the new ones and leaves the old ones still moving.

A full kit covers every mounting position on the vehicle, with the different shapes and heights each position requires, since mounts are rarely identical from front to rear.

New bolts and sleeves are usually included, which matters because the originals are frequently seized or corroded and are not worth reusing on a joint carrying the body.

Check the kit covers your cab configuration, since the number and position of mounts changes between body styles on the same platform.

Body Mount Chops and Clearance

Worth mentioning since it comes up alongside these parts.

A body mount chop is a modification where part of the body mount bracket is cut away to create clearance for a larger tire at full lock, common on body on frame off road builds.

It is a different operation to replacing the bushings, and the two often happen at the same time since both involve working at the same point on the vehicle.

If a chop is planned, doing the mounts at the same visit makes sense. Both require access to the same area and one of them involves cutting.

Body Mount Bushings and Lift Kits

Body lift kits use these same mounting points, which is worth knowing if both are on the list.

A body lift raises the body off the chassis using taller spacers at each body mount, gaining clearance in the wheel wells for larger tires without touching the suspension.

Because the spacers go in at the same locations as the bushings, the two jobs overlap almost entirely. Doing a body lift on collapsed mounts means lifting a body that is still moving, and the result feels worse than it should.

Where a lift is planned, fitting new mounts at the same time costs little extra labor and gives the lift something solid to sit on.

Longer bolts are required either way, since the spacer adds to the stack and the originals will run short on thread.

Where Body Mounts Sit in a Build

Worth understanding where these fall relative to everything else, since they are rarely the first purchase.

Suspension bushings control how the wheels are located. Engine and transmission mounts control how the drivetrain is held. Body mounts control how the structure those things attach to behaves.

That makes them the last link rather than the first. A car with tired control arm bushings gains more from fixing those, since the movement there is closer to the tire.

Where body mounts earn their place is on a vehicle where the suspension and drivetrain have already been addressed and the remaining vagueness is coming from the structure itself.

On an older body on frame vehicle they are frequently overdue regardless, since original rubber at high mileage has usually collapsed.

And on a rear drive car fighting wheel hop, rear subframe bushings often deliver more than another round of suspension parts.

Checking Body Mounts Before Ordering

A few checks tell you whether these are the problem.

Look at each mounting point along both chassis rails with the vehicle on a hoist. Collapsed rubber is visible as a reduced gap, bulging material or a washer sitting against metal.

Compare them side to side and front to rear. Mounts rarely collapse evenly, and the ones nearest heat sources usually go first.

Check the panel gaps and how the doors operate. A body sitting lower on failed mounts changes every aperture, and doors that have become harder to close are a reliable sign.

Listen out for the creak as you go over bumps. A body moving on collapsed mounts makes a distinctive groan over driveways that does not sound like suspension noise.

On a unibody car, look at the rear subframe mounting points for cracked rubber and for any witness marks showing the subframe has been moving against the body.

Replacing Body Mount Bushings

This is a bigger job than most bushing work, and the approach matters.

The body has to be lifted slightly off the chassis to get each mount out, which means supporting it safely across several points rather than at one.

Work on one mount at a time rather than several. Lifting the body at several points simultaneously puts stress into a structure that was never designed to be supported that way.

Expect to find at least some seized bolts. The through bolt runs down into the chassis and collects water, so penetrating fluid applied well in advance is worth the forethought.

Subframe bushings on a unibody car need the subframe supported and usually a press or a dedicated subframe bushing removal tool, since they sit in a closed housing with no access behind.

Torque everything to specification once the body is back down, and check panel gaps and door alignment before calling it finished.

Find Body Mount Bushings for Your Vehicle

Body mount bushings belong to our bushings lineup.

Select your vehicle to see the body mount bushings and subframe bushings available for it. Replace them as a complete set rather than individually, since a body held firmly at some points and loosely at others is worse than one held consistently.