A suspension lift is a modification, often done by Jeep, truck, SUV and offroad enthusiasts to raise the ride height of their vehicle. Suspension lifts (also referred to as lift kits or leveling kits) enable steeper approach, departure, and breakover angles, higher ground clearance, and helps accommodate larger wheels and tires. Due to the raised center of gravity, maximum safe operating angles are reduced and roadholding is often significantly impaired with a lift kit.
Each manufactured vehicle usually requires a specific lift kit, and the types of kits vary based on the type of drivetrain that the vehicle has. Kits can be as simple as lift blocks (spacers placed between the axles and leaf springs) and coil spring/strut spacers and extended shocks; to replacement control arms, trailing arms, and custom four-link systems. Suspension lifts also impact other factors, such as drive shaft length, steering geometry and brake lines. Legality is often an issue when installing suspension lifts, as many jurisdictions have varying laws on vehicle ride height and placement of lights and bumpers.
Suspension lift Wikipedia
Many trucks are supported by leaf spring suspensions. Leaf springs offer exceptional articulation, a large payload and can take a substantial amount of abuse. With the correct methods they can be modified to help a vehicle carry more weight, have better articulation or to fit large oversized tires. Some vehicles may be equipped with front and rear leaf springs or just rear leaf springs with independent front suspension.
Some methods of lifting are good for the rear, but not for the front, such as lifting blocks. Lifting the rear with blocks is a common way to achieve the desired height. This is done by installing a block, of the desired height of lift, in between the leaf spring and leaf spring perch and installing longer U-bolts. It is a bad method for the front primarily because of safety issues while braking. When braking, the front wheels create the majority of the braking force. The block moves this lateral force, caused by braking, higher above the axle than it did in the stock form. This can cause the block to become displaced from its location and result in total loss of control. For further explanation see this link;.
A more accepted way to build up the leaf springs is by using an add-a-leaf. This is done by inserting an extra leaf into the vehicle's leaf pack. Using the add-a-leaf will increase the height, but sometimes makes the suspension ride rough because of the added spring rate. A complete description of how this is done is shown at this link; . With an adequate budget, the best way to lift with leaf springs is to buy a new set with the lift built in. When using an add-a-leaf you are relying on the integrity of the old springs. They may be a bit worn out, so when the lift is installed, the proposed 2 inch leaves may only have lifted the truck 1.5 inches. The new leaf spring pack will not be fatigued and will give the "true" lift desired. These packs can be bought at various increments of lift and can be combined with lifting shackles to give the proper set-up.