Landing Gear That Will Not Crank
A jammed, stripped or bent landing gear leg strands a trailer at the dock. How landing gear fails, what to try before forcing it.
Landing gear is the part of a trailer everyone forgets until the crank will not turn. Then it is a dropped trailer that cannot be hooked, or a hooked trailer with legs still down that cannot move, and somebody is standing at a dock in Pensacola with a schedule falling apart. It is a mechanical failure like any other, and most of it can be fixed where the trailer sits.
Here is how landing gear goes wrong, what a driver can safely try, and where the line is between a little persuasion and doing real damage.
How landing gear works
Two legs, a crossshaft connecting them, and a gearbox on one leg driven by the crank handle. The gearbox has a high gear for running the legs up and down quickly with no load and a low gear for lifting the trailer. Inside each leg is a screw, a nut, and a set of bevel gears. Everything is greased, or is supposed to be, and everything is exposed to road spray, salt on the trucks that come down from the north, and the occasional curb or landscape timber.
The reasons it will not crank
- Wrong gear. The crank is in low gear with the trailer unloaded, or high gear with weight on the legs. Shifting the gearbox is the first thing to try, and a surprising number of stuck landing gear calls end there.
- Trailer weight is pinning the screw. If the fifth wheel is not carrying the trailer, the legs are, and low gear with real effort is what it takes. On a hot loaded trailer the crank can be very hard to turn.
- The crossshaft has slipped or the pin has sheared. The crank spins the gearbox leg but the far leg does not move. The trailer sits tilted and one leg is stuck.
- Dry or corroded screw. The nut has seized on a screw with no grease. Forcing it strips the gears.
- Bent leg. Somebody drove off with the legs down, backed into something, or dropped the trailer on uneven ground. A bent leg will not retract and may not extend.
- Stripped gearbox. The bevel gears or the input gear have lost teeth. The crank turns freely or grinds and nothing happens.
What to try before forcing it
- Confirm the gearbox is in the right range. Push or pull the crank to shift and try again.
- Take the weight off. If you are hooked, dump the tractor air suspension slightly or air it up, whichever unloads the legs. Sometimes the trailer just needs to sit an inch differently.
- Check the crossshaft. If one leg moves and the other does not, look for a sheared pin or a slipped coupling at the crossshaft. Do not keep cranking; you will twist one leg down and lift the other.
- Grease it. A dry screw on a leg that has not moved in months may free up with grease at the fitting and a little back-and-forth.
- Look for damage. A bent leg or a cracked bracket is a stop. You are not going to crank through it.
A cheater bar on the crank is how gearboxes get stripped. If it will not turn with normal effort in the right gear, something is wrong and force makes it worse.
The drive-off
The most expensive landing gear failure is the one where the driver pulls out with the legs down. The legs catch the pavement or the dock plate and fold, and the trailer's frame rails and the mounting brackets can go with them. If it happens, stop immediately. Do not try to raise the legs and do not back up. Get the trailer supported and get someone to look at it before it moves. Damaged landing gear on a loaded trailer at a dock can be replaced on site by a crew with the right legs and the trailer safely supported.
What the crew does on site
Diagnose the leg, the gearbox, and the crossshaft, free what can be freed, and replace what needs replacing. Crossshaft pins, crank handles, gearboxes, and complete landing gear legs are all jobs done where the trailer is. The crew supports the trailer properly before anything comes apart, and if the trailer is dropped and unhookable, the job includes getting it high enough to couple. It is the kind of work a fleet mobile repair call covers, and a normal part of the trailer service the truck handles.
Keeping landing gear working
Grease the legs and the gearbox at every service. Run the legs through their full travel occasionally on trailers that sit. Drop trailers on hard, level ground with sand shoes or pads under the legs on anything soft. And make the leg check a habit before every pull-away, because the drive-off is the one failure that costs more than the whole landing gear assembly.
Frequently asked questions
Can I drive with one leg stuck down?
No. It will catch on the first grade crossing or dip and fold. Get it raised or get it fixed first.
The crank spins but nothing happens. What is that?
Either the gearbox is stripped or the crank handle has sheared its pin. Pull the crank and look at the input shaft. If it turns freely with no resistance, the gearbox is gone.
Can landing gear be replaced at a dock?
Yes, with the trailer properly supported. The crew brings the legs and does it on site.
Why is the crank so hard to turn on a loaded trailer?
Because the legs are lifting the trailer. Use low gear, make sure the screw is greased, and if it is still unreasonable, something is bent or dry.
Trailer stuck at a dock or dropped in a yard anywhere from Crestview to Pensacola? Call Duckett Roadside Repair at (850) 495-0366. Dispatch answers 24 hours a day.