How We Inspect a Used Truck-Mounted Crane: Outriggers and Winch Matter Most
In Dongguan I looked at two 8-ton truck-mounted cranes. One outrigger sagged 9 mm over a 30-minute pressure hold — we took it with a 3,000-yuan discount. The other had broken rope strands, a re-welded crack, and a clocked odometer; we passed even at 20,000 off.
On November 26th, in Dongguan, a logistics customer was selling two truck-mounted cranes and asked me to come look at the goods. Eight-ton cranes mounted on Dongfeng chassis, 2017 models.
The customer was upgrading to new trucks and needed the two old ones out of the yard. The seller came through an acquaintance and the asking price wasn't crazy, but a truck-mounted crane gets inspected by the book no matter how familiar the seller is.
A truck-mounted crane is a truck plus a crane — half the inspection is the chassis, half is the crane. Plenty of buyers only look at how much the crane can lift, and end up with a dead chassis under a good crane, which makes the whole thing scrap.
That day I inspected two units and took one. They sat side by side in the yard, looking about the same — both freshly repainted. Appearance matters least; the truth of these machines hides in the outriggers, the winch, and the welds.
This piece is about the inspection method, with the focus on outriggers and the winch.
Outrigger cylinders: hold pressure for thirty minutes
Truck-mounted cranes have small outriggers and thin cylinders, which leak easily. The test: fully extend the outriggers, jack the rear of the truck off the ground, hang a half-ton load on the boom, and hold pressure for thirty minutes.
Mark the piston rods with a marker, then measure after thirty minutes. More than 3 mm of sink means internal leakage. On the first truck, the right-rear outrigger dropped 9 mm, and there was a ring of oil stains on the cylinder barrel — the seal was weeping.
A weeping outrigger goes soft during lifts. One millimeter of give and the boom sways a notch; swaying under load is scary stuff. A full cylinder assembly for that outrigger costs 4,600 yuan; a seal kit alone is 380. But if the barrel is scored, new seals won't fix it — you have to pull it apart and look.
Winch wire rope: feel every meter
Spool out the whole rope, put on gloves, and run your hand along it end to end. Broken strands, flat spots, kinks — your fingers beat your eyes.
The standard: within a length of six times the rope diameter, broken wires shouldn't exceed 5% of the total. The first truck's rope was fine. On the second, at the seventeen-meter mark, I felt a clump of burrs — six broken wires in one strand. That spot sits exactly where the load falls when the boom is fully extended.
A replacement rope isn't expensive — 1,200 yuan a roll for an 8-ton crane. But broken wires mean it's been overloaded, or the sheave grooves are worn. I followed up and checked the pulleys: the grooves had worn to sharp edges that cut rope. Swap the rope without the sheaves and the new rope is ruined in three months.
Don't forget the winch reducer either. Start the truck and hoist the empty hook, and listen for a sandy grinding sound — that means dry or worn bearings. The first truck sounded clean; the second had a faint rattle, which went into my notebook.
Boom welds and pins
The boom on a truck-mounted crane is a folding knuckle boom with lots of welds. Bring a small hammer and tap the welds — a crisp ring means solid metal; a dull thud can mean a crack.
On the second truck, the root weld of the second boom section sounded dull. I sanded off the paint and found a two-centimeter crack — re-welded, ground down, and hidden under body filler. A knuckle-boom crane with a crack history isn't worth taking at any price.
Check the pins for play too. If the connecting pins between boom sections are loose, the boom droops, and all precision is gone — you couldn't set a beam in place if you tried.
The chassis gets inspected like a truck
After the crane, the truck. Cold-start the engine and listen; shift through the gearbox and feel for jerks; watch how many minutes the brake air pressure takes to fall from nine bar to six.
The first truck's chassis had 230,000 km. The engine sounded right and the clutch had half its life left — acceptable. The second showed 80,000 km on the dash, but the tires, brake discs, and seat wear didn't match. The odometer had been rolled back. I don't touch clocked trucks.
One more thing people forget: the PTO. The crane's power comes off the gearbox through the power take-off. Engage the crane gear and listen for grinding teeth. On the second truck it clunked going in — rough engagement, and fixing that means pulling the gearbox, which isn't cheap labor.
Paperwork needs checking too. The registration certificate, driving license, and nameplate — match the VIN across all three. Truck-mounted cranes also carry special-equipment inspection records. The second truck's record had a one-year gap last year — another mark against it.
How the two trucks ended up
Truck one: leaking outrigger seal. We negotiated 3,000 yuan off and took it. Fix the leak with a new seal kit — cost, 380 yuan.
Truck two: broken strands, cracked weld, clocked odometer — the full set. The seller offered 20,000 off. I said no. Buy a truck like that and you don't sleep at night.
One line to remember when inspecting a truck-mounted crane: hold pressure on the outriggers, feel the rope to the last meter, tap and listen to every weld, and treat the chassis like a truck. Miss one item, lose one deal.