Landing Gear Maintenance: Preventing Failures During Drop and Hook Operations

How Landing Gear Works and Why It Fails

Landing gear supports the front of the trailer when it is not connected to a tractor. The system consists of two retractable legs with foot pads, a crank mechanism that raises and lowers the legs, a gear system that provides high-speed (fast descent with low effort) and low-speed (slow movement with high lifting force) operation, and cross-shafting that connects the two legs to a single crank handle for synchronized operation.

Landing gear fails from three primary causes: corrosion that seizes the internal gears and leg tubes, lack of lubrication that causes premature wear on gears and bushings, and physical damage from dragging on the ground, hitting obstacles, or operating on unstable surfaces. In drop-and-hook operations where the landing gear is used multiple times daily, wear accelerates significantly compared to trailers that stay coupled for weeks at a time.

A landing gear failure during a drop operation can have serious consequences. If the legs collapse or fail to lock, the trailer nose drops to the ground, potentially damaging the trailer, the landing gear assembly, air and electrical lines, and creating a dangerous situation for anyone nearby. If the legs fail to retract fully, they can drag on the road during transit, causing sparks and progressive damage.

Inspecting Landing Gear Components

Visual inspection starts with the leg tubes and foot pads. Check for bent or twisted legs (indicating the trailer was dropped on uneven ground or the legs took a lateral impact), cracked welds at the mounting bracket where the legs attach to the trailer frame, missing or damaged foot pads (the flat plates at the bottom that distribute weight), and the extension tubes for smooth operation (they should slide in and out without binding).

Crank operation testing reveals internal problems. Operate the crank handle through a full cycle: extend the legs fully, retract them fully, and note any resistance, grinding, popping, or slipping. Excessive resistance indicates corrosion or lack of lubrication in the gears. Grinding suggests worn gears. Popping or slipping indicates the gear selector mechanism is not engaging properly between high and low speed.

The gear selector mechanism switches between high-speed (for quickly lowering empty legs to the ground) and low-speed (for lifting the loaded trailer nose off the fifth wheel). Test both speeds by engaging each position and cranking. In low speed, the crank handle should turn with moderate effort and the legs should move slowly but with strong force. In high speed, the crank should turn easily with the legs moving quickly but with less lifting force.

Cross-shaft integrity ensures both legs move together. With the landing gear partially extended, attempt to move one leg independently of the other. Any independent movement indicates a broken or disconnected cross-shaft, which means only one leg operates when you crank. A single-leg landing gear operation is unstable and dangerous. Cross-shaft repair involves accessing the internal shaft through the cross-tube housing.

Lubrication and Corrosion Prevention

Lubricate landing gear every 30 days for trailers in regular drop-and-hook service, or every 90 days for trailers that stay coupled. The internal gears, leg tubes, and cross-shaft all require lubrication to operate smoothly and resist corrosion.

Apply grease through the grease fittings on the landing gear housing (typically 2 to 4 fittings). Pump grease until it purges from the gear housing seals, confirming the grease has reached the internal components. If grease does not purge, the fittings may be clogged or the internal passages may be blocked with dried grease or corrosion.

The leg tubes (inner and outer) should be lubricated with a light coating of grease or a corrosion-inhibiting spray. Extend the legs fully, clean the exposed tube surface, apply lubricant, and retract. This distributes lubricant on the sliding surfaces and protects the exposed metal from corrosion. In salt-belt states, this treatment should be done monthly during winter.

The crank handle and shaft should be lubricated at the pivot and where the handle connects to the gear input shaft. Dry crank mechanisms are difficult to operate and wear prematurely. A drop of penetrating oil on the crank shaft pivot and the gear engagement mechanism keeps operation smooth.

Water displacement spray (WD-40 or equivalent) applied to the gear housing exterior, cross-tube, and mounting brackets after washing prevents surface corrosion that progresses to structural damage. Landing gear assemblies exposed to road spray and salt are especially vulnerable to corrosion that attacks the mounting bracket welds and the thin-wall leg tubes.

Common Landing Gear Repairs and When to Replace

Crank handle replacement is the most common landing gear repair. Handles bend from excessive force, break from metal fatigue, and the internal gear engagement mechanism wears from repeated use. Replacement handles cost $30 to $80 and can be installed in 15 to 30 minutes. Keep a spare crank handle in your tool kit because a lost or broken handle strands the trailer in the dropped position.

Gear replacement is needed when the internal gears strip, crack, or wear to the point where they slip under load. Gear kits cost $100 to $300 depending on the landing gear manufacturer and model. Gear replacement requires removing the gear housing cover, extracting the old gears, and installing new gears with proper alignment. This repair is typically performed by a shop but can be done roadside with the right tools and knowledge.

Leg tube replacement addresses bent, cracked, or seized legs. Individual leg assemblies cost $200 to $500. In severe cases, the entire landing gear assembly (both legs, cross-shaft, gears, and mounting bracket) needs replacement at $500 to $1,200. Complete assembly replacement is often more cost-effective than replacing multiple individual components on an old landing gear.

Foot pad replacement or addition prevents the legs from sinking into soft ground. Standard foot pads can be supplemented with larger pads ($15 to $40) for operations that frequently drop trailers on unpaved surfaces. Sand shoes (oversized flat pads) distribute the trailer nose weight across a larger area, preventing the sinking that bends legs and damages the gear mechanism.

Best Practices for Landing Gear in Drop-and-Hook Operations

Before dropping a trailer, ensure the landing gear legs are fully extended and the foot pads are firmly on a solid surface. If the ground is soft (gravel, dirt, wet asphalt), place boards or landing gear pads under the foot pads to distribute weight and prevent sinking. Never drop a loaded trailer on a surface that will not support the nose weight (typically 12,000 to 25,000 pounds).

The proper drop sequence is: set the trailer brakes, lower the landing gear until the pads firmly contact the ground, continue cranking in low speed until you feel the trailer nose begin to lift off the fifth wheel (this confirms the legs are supporting the weight), pull the fifth wheel release handle, and slowly pull the tractor forward while monitoring the trailer. The trailer should remain stable and level as the tractor separates.

When hooking to a dropped trailer, verify the landing gear is fully retracted before driving away. Partially retracted legs that hang below the trailer frame will contact the road surface, creating sparks (a fire hazard near fuel stations) and damaging the legs and foot pads. Double-check retraction by looking under the trailer from behind after cranking the legs up.

In cold weather, landing gear mechanisms can freeze from moisture inside the gear housing. If the crank will not turn after the trailer has been sitting in freezing conditions, do not force it with a pipe extension because this strips the gears. Instead, apply penetrating oil to the gear housing and crank mechanism, wait 10 minutes, and try again. If still frozen, apply heat (a heat gun, not an open flame) to the gear housing to melt the ice.

Train all drivers who handle your trailers on proper landing gear procedures. A single incident of dropping a trailer with the legs improperly positioned or on inadequate ground can cause $1,000 to $5,000 in landing gear damage. The 2 minutes spent ensuring proper setup saves hours of repair time and significant expense.