What to check on a used mixer

The drum

The drum is the truck's whole job. A tired chassis can still get you to the site; a tired drum costs you on every load.

• Fins. Look in from the head and at the discharge end. The spiral fins inside do the mixing on the way in and push the load out on the way back. When they wear down, discharge slows and the last part of the load can hang up. Worn fins aren't a deal-breaker, but they mean a reline, so price it in.
• Buildup. Hardened concrete inside is dead weight you haul on every trip, and it eats into the yards you can carry. Ask when it was last chipped out.
• Shell. Look for thin spots, patches and cracks, especially around the head and the roller track. The shell takes a beating every turn.
• Rollers and track. Spin the drum and watch it. It should turn true. A drum that wanders or thumps usually has flat rollers or a worn track, and that shows up here before anywhere else.

Drum drive

The drum is turned by a hydraulic pump and motor through a gearbox. When this system is healthy you barely notice it.

• Run the drum both directions at idle and at speed. It should start, stop and reverse without a clunk. A clunk on reversal is the drive telling you something.
• Check the pump, motor and gearbox for leaks and for whine. A little seep is common on an old truck; a wet gearbox is a conversation.
• Look at the hoses. Cracked or weeping hoses are cheap to replace in the yard and expensive to lose halfway through a pour.

Chute and hopper

This is where front discharge earns its keep: the driver places the concrete from the cab, so the chute has to answer the controls.

• Work the chute from the cab: up, down, side to side. It should move smoothly and hold position without drifting.
• Check the hopper and chute liners for wear-through. Concrete is abrasive and liners are a wear item.

Water system

Water is how a driver adjusts slump on site and washes out after the pour. A weak system makes both harder.

• Fill the tank, pressurize it and run water through the hose and into the drum.
• Listen for air leaks at the tank and valves. The tank runs on air pressure, so a leak there is easy to hear if you listen for it.

Frame, axles and brakes

A loaded mixer is one of the heaviest things on the road. The frame and running gear carry all of it.

• Frame rust and cracks, especially around the drum pedestal mounts and crossmembers, where the drum's weight and twisting load go into the frame.
• Lift axles: raise and lower each one, and check the air bags and controls. A lift axle that won't come down changes what the truck can legally carry.
• Air brakes: build pressure, shut it down and watch the gauge. A slow leak-down is normal on an old truck; a fast one is not.
• Tires: tread depth, matched duals and sidewall cuts. Mismatched duals wear each other out.

Engine and transmission

Most mixers spend their lives at low speed under heavy load, which is hard on the drivetrain in its own way.

• Cold start if you can. Watch for smoke and listen to it settle. A truck that's been warmed up before you arrive is hiding its first minute.
• Have your mechanic read the codes, and check for blow-by at the oil fill.
• Shift through every range. Allison automatics store codes too, so have those pulled as well.
• Know the emissions year. Some fleets and jobs have rules about older engines, so check yours before you buy.

Paperwork

The paper tells you how the truck was kept, and whether it's really the truck being sold.

• Ask for the service records and read the last two years. Regular service is a better sign than low miles.
• Match the VIN on the title to the frame and the door tag.
• Check your state's weight rules and permits for the axle setup you're buying.

Words worth knowing

Front discharge

The drum unloads over the cab instead of off the back, and the driver works the chute from the seat. One person can place the pour, which is why small crews like them.

Fins

The spiral blades welded inside the drum. They mix the load on the way in and drive it out on the way back.

Reline

Rebuilding the worn fins, and sometimes sections of the drum shell, so the drum mixes and discharges like it should.

Glider

A new chassis and cab built on a drivetrain taken from an older truck. You get newer sheet metal and frame on a proven engine and transmission.

Lift axle

An extra axle that lowers to spread a heavy load and raises when the truck is empty, saving tires and fuel.

Duals

Two tires side by side on each end of an axle, carrying more weight than a single tire.

Slump

How stiff or loose the concrete is. Drivers adjust it on site with water from the truck's tank.

That's the walkaround. If you're looking at one of our trucks, every listing says what we know and what needs work. If something on this list isn't covered, ask. We like these questions.

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