Subframe Buyer’s Guide
- The subframe is a component in your vehicle's chassis.
- This component is a separate structure within a significantly larger monocoque or body-on-frame shell where the engine, drivetrain, suspension, and steering components are housed.
- A subframe has three basic forms, all of which have varying functions.
- These are the simple axle type, the perimeter frame which supports the engine, and the perimeter frame which supports the engine, transmission, and full suspension.
- A subframe and crossmember have similar functions, but they are not interchangeable.
- Structurally, a subframe can include a crossmember. A crossmember, on the other hand, can’t contain a subframe within it.
- Additionally, in cars with a full chassis, separate rear and front subframes help reduce their overall weight and subsequent cost. With a subframe, subassemblies can be introduced to the main body shell when needed.
- When damaged, the subframe can result in unusual vibrations and harshness as you drive. If left unattended, these issues could result in long-term problems that could impair your car's drivability.
Cars are usually built with a frame that is meant to hold everything together. Within this structure is a component integral to the overall function of your vehicle. This component is called a subframe. The subframe carries significant parts within it, such as your engine, suspension, or drivetrain.
When damaged, the subframe can result in unusual vibrations and harshness as you drive. If left unattended, these issues could result in long-term problems that could impair your car's drivability. Read on to learn more about subframes, their functions, and when to have them replaced.
What is a subframe?
The subframe is a component in your vehicle's chassis. This component is a separate structure within a significantly larger monocoque or body-on-frame shell where the engine, drivetrain, suspension, and steering components are housed. Simply put, it supports the integral parts contained within your vehicle.
The car subframe is typically constructed from welded steel tubing or thick pressed steel panels. How the subframe is attached depends on the vehicle type, but it is usually bolted or welded. A bolted subframe is fitted with springs or rubber bushings to dampen the vibrations produced while on the road. It can also be hydroformed.
How does a subframe work?
Primarily, the subframe supports integral components within your vehicle's chassis. It's there to give the chassis rigidity. Its main purpose includes isolating vibrations and harshness from the rest of the body, as well as spreading high chassis loads over the vast expanse of relatively thin sheet metal of a monocoque body shell.
With a subframe, the force produced by the engine and transmission is significantly reduced. It will have lessened enough that drivers and passengers are guaranteed a smooth ride. Once the subframe malfunctions, however, the drive is anything but.
Why is a subframe important?
The subframe is important because it makes building the engine, transmission, and steering assemblies possible in one location. It also allows you to install these finished pieces into a different place in the vehicle. Having a subframe enables your car to spread high chassis loads over a wide area of its body shell. It also strengthens your vehicle's body with an independent front suspension, a front sway bar, disc brakes, and an improved engine.
Additionally, separate rear and front subframes in cars with a full chassis help reduce their overall weight and subsequent cost. With a subframe, subassemblies can be introduced to the main body shell when needed.
Basic forms of the subframe
A subframe has three fundamental forms, all of which have different functions. They include:
Simple axle type
This type of subframe usually carries the steering rack and the lower control arms of your vehicle. Axle subframes must be stable to ensure excellent road contact, but it still has to be light to guarantee high occupant comfort regardless of surface unevenness. Axle subframes can be used on the front or rear ends of your vehicle.
Perimeter frame that also supports the engine
This kind of subframe supports your car's engine, lower control arms, and the steering rack. It is larger than a simple axle type subframe so it can support more components.
Perimeter frame that also supports the engine, transmission, and full suspension
This type of subframe is usually found on front-wheel-drive cars. It is a perimeter frame that supports your car's engine, lower control arms, steering rack, transmission, and even full suspension.
Because of its use and location, a subframe is often mistaken for another component, the crossmember.
Subframe vs. crossmember
A subframe and crossmember have similar functions, but they are not interchangeable. Structurally, a subframe can include a crossmember. A crossmember, on the other hand, can't contain a subframe within it. A subframe is larger and covers more surface on the underside of your vehicle.
Like the subframe, the crossmember is also a significant structural component of your vehicle. It is a steel, boxed piece bolted across the underside of your car. This component supports the transmission and the internal combustion engine. The crossmember also acts as a brace, helping your vehicle maintain stability and keep it from shaking.
In contrast, a subframe provides a protective cradle for the engine and attachment points for the suspension. It can support anywhere from the engine and suspension, to the drivetrain. A crossmember is usually found in unibody vehicles.
Symptoms of a bad subframe
If your subframe malfunctions, your car's drivability will significantly be affected. As the subframe supports integral components within your car's chassis, it should be regularly maintained. Here are some subframe damage symptoms you should look out for.
Like any other vehicle part made of steel, subframes are prone to rust. Rust corrodes the metal, so when the structural support for most of your vehicle's chassis falls apart, you're left with a shaky, unstable vehicle. Rust can diminish your car's handling and directional stability substantially. When rusty parts break off or fall apart, you can expect dramatic toe angle changes and highly variable response to steering inputs.
Subframes are prone to misalignment, causing vibration and alignment issues in the suspension and steering components. Misalignment is caused by space between the chassis-subframe mounting bolts and the mounting hole. Make sure your subframe is mounted correctly to avoid loose parts.
Unusual or excessive vibration and harshness
A broken, damaged, or corroded subframe results in unusual or excessive vibration and harshness when driving as the engine and everything else it is supposed to be supporting becomes unstable.
For the suspension of any car to operate as it should, for proper handling, and to keep the body panels in alignment, the frame must be strong enough to cope with the loads applied to it. It must not deflect, and it has to have enough torsional strength to resist twisting.
If you experience directional stability problems or unusual or excessive vibrations and harshness while driving, this could point to a failing subframe. Once this happens, your car might need more than just a subframe repair. Your best option would be to replace your subframe entirely.
How much does a subframe replacement cost?
A subframe replacement costs anywhere from around $100 to $600, depending on your vehicle's type, year, make, and model. The location of your subframe can also affect its cost. For example, front subframe replacement costs could vary from subframes located on the passenger side, the driver side, or the rear.
Finding the right fit
When buying a subframe, make sure it fits the specification of your vehicle. Get the right subframe for your vehicle by entering its year, make and model into our search engine. You can also filter your search according to your preferred brand, price range, or subframe location. Just click search and browse through our selection of high-quality subframes.
Do-It-Yourself Subframe Installation Guide
Have you been experiencing unnecessary vibration and harshness when you are driving your vehicle? If your answer is a resounding ‘yes,' then you may want to consider replacing your Subframe. The Subframe enables your vehicle to spread high chassis loads over a wide area of your body shell. It will also strengthen your vehicle's body by adding an independent front suspension, a front sway bar, disc brakes, and an improved engine. However, if you are thinking of replacing the subframe on your own, you must ensure proper placement and measurement to ensure that it will be properly installed. It also requires special tools and skills. If you're up for it, then follow these steps.
Difficulty level: Moderate
What you'll need:
- Jack and jack stands
- Plasma cutter
- Welding equipment
- Protective glasses and equipment
- Replacement subframe
Step 1: Wear protective equipment to ensure safety while installing your subframe. Raise your vehicle evenly at all four corners. Use a floor jack and jack stands to ensure that your vehicle will be secured as you perform the installation.
Step 2: Cut the original frame by a few inches in front of the firewall using a plasma cutter. Make sure that your vehicle stays in place as you cut the frame. You might need help in doing this, especially if you haven't tried cutting metal before.
Step 3: Put the new subframe under the old chassis. Level the subframe relative to your vehicle, and mark the height of the subframe. It depends if you want to lower your vehicle.
Step 4: Trim the original frame to match the curve of the subframe. Place the subframe relative to the rest of the frame. To ensure accuracy, make sure to take measurement and level the subframe based on the old frame and not to the body.
Step 5: This part is one of the more difficult steps. Use three hanging bobs to position the F-body subframe accurately. Remember to take the right measurements, even if it takes you a long time.
Step 6: Once the subframe is in place, trim the excess metal from both frames. Afterwards, temporarily weld the subframe in its correct position.
Step 7: Check the measurements again before you butt-weld the frames together. Weld small sections one at a time and double-check the measurements as often as you can.
Step 8: You may choose to paint over the subframe parts that you have welded to make it look natural.
Step 9: Reconstruct the front sheet metal mounts, the radiator core support mount, the bumper mounts, and the steering shaft.
Step 10: Make sure that all the parts that you removed will be reinstalled properly. This is important to gauge if you were able to install your subframe properly.
It would take you at least two hours to install a new subframe. It would help if you can ask someone to assist you during the installation. However, it is recommended that you bring your vehicle to an expert mechanic to install your subframe.