What are the functions of a leaf spring on my Ford Transit?

Despite its name, a leaf spring serves multiple purposes. Its main function is to link the axle and chassis, making it a crucial component. Consequence: If the leaf spring, particularly the main spring leaf, is broken or missing, the axle is not properly fixed to the chassis. In extreme cases, the axle may even move out of position, causing the vehicle to lose control on the road.  

The leaf spring is responsible for keeping the axle in the correct direction. As a result, if the leaf spring does not have the correct dimensions, or especially if there are leaf springs with different dimensions on the left and right sides, the axle will not be parallel and the vehicle's driving conditions will be negatively affected. For example, there may be excessive tire wear or the vehicle may pull to the left or right.

The leaf spring is a crucial component of the suspension system, which typically includes the following main parts:

• Leaf spring

• Shock absorber

• Bump stop

• Stabilizer bar (optional based on different models and axle load categories)

The suspension system is composed of these parts, which work together to maximize tire-road contact, provide stability and good handling, evenly support the weight of the vehicle, and ensure passenger (and cargo) comfort by absorbing and dampening shocks.

 

Are leaf springs old-fashioned solutions?

Although leaf spring suspension is over 150 years old, it is not outdated. Leaf spring technology has developed significantly, especially in the last 40 years with the invention of the so-called parabolic leaf spring. Leaf springs remain the most efficient suspension for commercial vehicles. Recently, there has been intensive development in leaf spring materials, with new materials such as high-stress spring steels and composite materials being implemented.
Leaf springs are commonly used in the following vehicles nowadays:

• Heavy-duty trucks and trailers: 60% - 70% of these vehicles having leaf springs on their axles (front and/or rear). Nowadays, 70% to 80% of these vehicles use parabolic leaf springs, while 20% to 30% use multi-leaf springs. The remaining vehicles have air springs.

• Light commercial vehicles 3-7 tons: 90% of these vehicles have leaf springs on the rear axles and 10-20% also on the front axles. Most of these vehicles are equipped with parabolic leaf springs, while the rest have either air springs or torsion springs.

• Pickup Trucks: 90% of successful pickup truck brands use leaf springs, mainly traditional multi-leaf springs.

What is the raw material (spring steel) of Ford Transit leaf springs?

The spring steels commonly used for producing leaf springs in modern European vehicles are:

• 51CrV4: contains 0,51% Carbon, 1,1% Chromium and 0,2% Vanadium (mainly for parabolic leaf springs)

• 55Cr3: contains 0,51% Carbon, 0,7% Chromium and 0,7% Manganese (mainly for conventional leaf springs depending on cross sections)
   

Why did the leaf spring break in my Ford Transit?

Leaf spring breakages in Ford Transit can have several causes, and it can be difficult to determine the exact root cause. However, the typical causes are listed below. Please note that these explanations are simplified for easy understanding. Leaf spring (suspension) technology and steel technology (metallurgy) are special sciences.

• Micro cracks on the surface can originate from production or mechanical damage during assembly or usage, such as when a stone hits from the road.

• Non-metallic inclusions are compound materials embedded inside steel during the manufacturing process. They have a different chemical origin and give different mechanical properties to steel, such as formability, toughness, machinability, and corrosion resistance. Producing spring steel and spring leaves without inclusions is difficult and expensive. If these inclusions are too large or too close to the surface of the spring leaf, the leaf spring may break after a certain period of time.

• Improper heat treatment process: When producing spring leaves, heat treatment is one of the final steps to ensure that the spring steel is in optimal condition. During this process, the spring leaves are slowly heated to 850-950 degrees Celsius, then quickly cooled in an oil bath to 45-55 degrees Celsius, and finally heated again to 400-500 degrees Celsius before being slowly cooled to room temperature. If this process is not executed properly, it can have several negative consequences.

• Surface decarbonization can occur when repairing leaf springs in a small forging shop. Heating the spring leaf in an open fire can cause significant carbon to burn out from the surface, leading to the formation of microcracks.

• Corrosion that begins on the surface of the steel will spread throughout the material.

• Breakage on the leaf spring center hole: U-bolts were not tightened to the specified torque.

• Breakage on the leaf spring eye may be caused by a production failure, worn leaf spring bushings, or corroded spring shafts.

• Continuous overloading of the vehicle.

• Intensive/extreme suspension usage due to poor road conditions.

• Design mistakes by vehicle manufacturers may occur when the leaf spring or suspension design is inadequate. Currently, manufacturers optimize leaf springs to reduce weight and material costs, which can compromise payload capacity.

• Overall, if the leaf spring on your Ford Transit is broken, you cannot blame yourself for any mistakes. However, you must purchase a new leaf spring as soon as possible.

 

Is it safe to drive a Ford Transit with a broken leaf spring?

There are six main criteria to consider when deciding whether you can drive your Ford Transit with a broken leaf spring.

1.     Where (in which position) did the leaf spring break?

2.     Is the leaf spring a single leaf or a spring pack with multiple leaves?

3.     If your spring has multiple leaves, which leaf is broken?

4.     Is your vehicle loaded or empty?

5.     Does your vehicle have a stabilizer bar?

6.     Are you willing to take a risk? (Consider the potential consequences of driving without a replacement.)

The most dangerous combination is when the single leaf (mono leaf) spring, or the main leaf of a spring pack, is broken between the axle and front fixing point, and the vehicle does not have a stabilizer bar. In this case, the vehicle's axle is not properly fixed to the chassis, and the leaf spring on the other side is under tension. As a result, the leaf spring on the other side may break at any time, causing the axle to unexpectedly move out of its proper position and potentially causing the vehicle to become uncontrollable. In such cases, the vehicle should be driven at a minimum speed and taken for urgent servicing.
In some cases, if the main spring leaf is not broken or if it is just another spring leaf that is broken, or if the main spring leaf is broken between the axle and the rear fixing point, the vehicle can still be used for a certain amount of time, but without carrying significant loads. In these situations, acceleration and braking should be done more carefully than usual.

Can a Ford Transit leaf spring be repaired with welding?

Unfortunately, while spring steels do have some weldability, the welding process can cause changes in the structure of the steel around the joint, resulting in a lack of homogeneity and consistency with the rest of the steel. A welded leaf spring will therefore break very soon (a few weeks).

What other problems can I have with my Ford Transit leaf spring?

Leaf springs can have problems, other than just breakages. 

• The main issue is usually that the leaf spring is too weak, causing the rear of the vehicle to sag or sway. Leaf springs wear out over time, typically after 5 to10 years. The solution is to replace the leaf springs.

• Weak leaf spring design is a common issue, especially when the vehicle is carrying its maximum payload or is constantly under load, such as vehicles with cranes, lifting panels, or camper vans. To address this issue, auxiliary suspension can be implemented, such as air springs, helper springs, or leaf spring reinforcing kits. Another solution is to replace the weak leaf spring with a stronger one.

• The leaf spring may weaken after a few months of use, which is often due to a production issue resulting from improper execution of the heat treatment process. The recommended solution is to replace the leaf springs, which is typically covered under warranty by the leaf spring manufacturers.

• Furthermore, leaf springs may produce squeaking noises during operation. This typically occurs when plastic or rubber parts between the spring leaves are worn or missing. Leaf spring bushes may also cause squeaking noises. However, the exact source of the squeaking noises from the leaf springs always requires further investigation. In some cases, such as with heavy truck leaf springs, squeaking noise cannot be avoided.

• Leaf spring suspensions may be too harsh for some users, especially if the vehicle is not carrying any cargo. While leaf spring suspensions have several advantages (see our article as a blog post), comfort is not their main feature. However, there are options to improve ride quality, such as implementing a weaker leaf spring and adding an auxiliary air spring system.
   

How can I select and order the correct leaf spring for my Ford Transit in this online shop?

Our Online Shop offers four options for selecting and ordering leaf springs for your Ford Transit:

• If you know the article number (OEM number) of the leaf spring, you can find it directly in the online shop. The article number is typically stamped into the spring. Alternatively, the leaf spring article number is painted on the leaf spring or there is a label with the leaf spring article number on it. This ensures that you order the right Ford Transitsit leaf spring with 100% certainty.

• Submit the data of your Ford Transit as an online inquiry. Based on the production year and VIN number, we will identify the appropriate leaf spring. This solution also gives you 100% certainty that you are ordering the correct leaf spring.

• To order the appropriate leaf spring for your Ford Transit, provide the production year and number of spring leaves. In rare cases, we may request that you email us your vehicle information as outlined in the previous section.

• If you measure the main dimensions of your Ford Transit leaf spring, such as length, thickness, width, and bending, we can offer a matching replacement. However, please note that even with these measurements, we cannot guarantee a 100% fit.

Note: If you are unsure whether the suspension (leaf spring) of your second-hand Ford Transit has been modified, you can send a photo of your current leaf spring.

Do I have to replace the leaf springs in pairs in my Ford Transit?

70% of our customers do not buy leaf springs in pairs and it rarely happens that they have to buy the 2nd leaf spring to the other side. However, it may be necessary to purchase Ford Transit leaf springs in pairs in certain cases:

•  The vehicle is old and the non-broken leaf spring is weak. If a new leaf spring is installed, it may be stronger than the old one and cause the vehicle to become unlevel.

• The vehicle was driven with a broken leaf spring for an extended period of time, causing the opposite spring to be under tension and at a risk of breaking soon.

• Companies that aim to reduce risk and minimize service downtime typically prefer to replace both leaf springs once the vehicle is in service.
   

Can I purchase a single spring leaf for my Ford Transit if it has a leaf spring with two or more leaves?

It is technically possible to purchase not only complete Ford Transit leaf springs but also single spring leaves from our company. To do so, please submit your vehicle data as an online inquiry and fill in the remark field accordingly.

 

Can I replace the leaf spring of my Ford Transit myself?
Replacing a leaf spring does not require specific knowledge, but it can be time-consuming if you lack experience. You will need several tools and must lift and secure the vehicle in a safe position. Our blog contains training videos on how to replace a leaf spring.

 

Importance of Proper Torque for Ford Transit Leaf Spring U-Bol