Landing gear will not crank, or a leg has folded: what to do and what not to do

How landing gear is meant to work

A semi-trailer has no front axle. When it is uncoupled from the tractor, the front of the trailer rests on its landing gear: two telescoping legs just behind the kingpin, joined by a cross shaft so that turning one crank handle drives both legs together. Each leg ends in a foot, often called a sand shoe, that spreads the load onto the ground.

Most landing gear has a two-speed gearbox. High gear moves the legs quickly when there is no weight on them, for lowering them to the ground or retracting them once the tractor is carrying the trailer. Low gear trades speed for force, and it is the gear meant for actually raising or lowering the loaded front of a trailer. A great deal of landing gear damage comes from forgetting that difference.

When the crank will not turn

When the crank will not turn, the cause is usually one of the following. Whatever it turns out to be, do not put a cheater bar on the crank handle to force a stuck leg: if the gear is stripped or the leg is bent, more force breaks more parts, and a handle that slips under that force can injure the person holding it.

• Seized from rust or dry. Landing gear that has sat for a long time, or never been greased, can seize solid. It is especially common on trailers that live outside and move rarely.
• Trying to lift a load in high gear. High gear does not have the mechanical advantage to raise a loaded trailer, and forcing it can strip the gears.
• Stripped gears. If the crank suddenly spins freely without the legs moving, gears inside the gearbox have usually stripped.
• A sheared cross shaft pin or bolt. If one leg moves and the other does not, the connection between the gearbox and the cross shaft, or the shaft to the far leg, has usually failed.
• A bent leg. A leg bent by an impact, or by the trailer being moved while the legs were down, can bind and refuse to telescope.
• Ice. Water inside the legs can freeze and lock them in cold weather.

When a leg has collapsed or the nose has dropped

• Dropped on soft or uneven ground. On a soft shoulder, gravel or asphalt softened by heat, one foot can sink or tilt, putting side load on a leg that was only built to be pushed straight down.
• The tractor pulled away too soon. If the tractor pulls out from under the trailer before the legs are fully down and bearing the weight, the nose drops onto whatever is below it.
• Legs not fully down. A trailer set down on legs only partly lowered puts extra strain on the leg tubes and the gearbox.
• Overload or impact. A heavily loaded nose, a load concentrated at the front, or a leg struck while backing or in a yard can fold a leg.
• Backing under at the wrong height. A tractor that backs under a trailer set too low can shove the trailer back and bend or break the legs.

Staying safe around a dropped or unstable trailer

A trailer resting on damaged landing gear can move without warning. A leg that has partly folded can fold completely, and a nose that is sitting on one good leg and one bad one can shift sideways. Nobody should go under the front of that trailer, reach into the landing gear, or stand where the nose would land if it dropped further.

Keep people clear, keep the tractor away unless the trailer is being deliberately supported by it, and tell dispatch exactly how the trailer is sitting: which leg has failed, whether the nose is resting on the ground, on the other leg or on something else, and whether the trailer is loaded. If the trailer is at a dock, tell the facility so nobody tries to drive a forklift into it.

That last point matters more than it sounds. A forklift driving into the front of an uncoupled trailer puts a heavy, moving load onto the landing gear exactly where it is weakest, which is why many docks place trailer stands under the nose of any trailer that is loaded or unloaded without a tractor attached. If a leg has already failed, those stands, or proper cribbing placed by the people lifting the trailer, are what keep the nose from dropping further while it is repaired. Nobody should improvise supports from pallets or scrap under a loaded trailer.

What gets fixed at the roadside or the dock

Landing gear problems are regular work for the trailer repair truck. Seized legs are freed and lubricated, stripped gearboxes are replaced, sheared cross shaft pins and bolts are replaced, and bent or broken legs are replaced on site. When a trailer's nose has dropped, it is lifted and supported safely first — by the front of the trailer's structure near the kingpin, never by the damaged landing gear — and the failed leg is then repaired or replaced while the trailer is properly supported.

A loaded trailer with a dropped nose is a lift-and-rig job as much as a repair, which is why our trailer repair and recovery work come from the same yard. The trailer repair page covers the landing gear and running gear faults we fix, and the winch-out and recovery page covers dock and yard mishaps where a trailer has to be lifted first.

If the problem is not the landing gear at all but a trailer that has to be moved without its tractor, read can a trailer be towed without its tractor, which covers what has to work before a trailer can travel.

Preventing the next one

Most landing gear failures trace back to a handful of habits:

• Grease it. Landing gear that is lubricated on a regular schedule seizes far less often, especially on trailers that sit.
• Use low gear under load. Switch to low gear before the legs take the weight of a loaded trailer, and when raising a loaded nose.
• Put pads under the feet on soft ground. Boards or proper landing gear pads spread the load on gravel, dirt, grass and hot asphalt.
• Get the legs fully down before uncoupling. Confirm both legs are down and carrying weight before releasing the fifth wheel and pulling away.
• Crank them fully up before driving. Legs left partly down can catch on a railroad crossing or a steep driveway and fold under the trailer.
• Check before backing under. Set the trailer height so the tractor's fifth wheel meets the trailer correctly rather than shoving it.

Related reading

Trailer Lights Not Working? Troubleshoot the Seven-Way — Most trailer light failures start at the connection between tractor and trailer: a corroded or loose seven-way plug, a worn pigtail cord, or a bad ground.

Trailer Brake Dragging or a Hot Hub: Roadside Fix or Tow? — A dragging trailer brake heats one hub, and a hot hub can end in a wheel-off or a fire.

DOT Out of Service: Faults That Freeze a Running Truck — An out-of-service order means the vehicle legally cannot move until the listed fault is repaired, even if it runs perfectly.