Checkpoint: How to buy a used tri-axle dump truck

When it comes to buying a pre-owned dump truck, Steve Thompson, director, used truck sales, Arrow Used Trucks, says two things are immensely important. “First, never trust an odometer,” he says. “No matter how reputable the seller or the dealer you’re working with, they don’t know for sure if it’s been dialed back, disconnected or broken in its past life. Low indicated mileage is great, but it’s no substitute for a thorough walk-around inspection and test drive.”

Second, Thompson says to make sure you get a warranty to protect your investment. “Unless you’re buying a 15-year-old truck from a friend for $5,000, you have a right to expect a warranty on a pre-owned truck,” he says. “And make sure you fully understand any warranty information offered to you. If there’s anything on a warranty contract you don’t understand, don’t sign the document.”

The cab tells the tale
Our sample rig was a 2000 model Mack RD 688 tri-axle dump. It’s equipped with a Fuller, eight-speed double low transmission and a Mack E7 350 engine. The truck’s hour meter shows 1,583 hours with 31,500 miles registered on the odometer. A quick walk-around reveals the truck is in excellent condition. Arrow has steam cleaned the rig and repainted it. “We put all our trucks through a rigorous 150-point inspection,” Thompson says. “So if this truck is on our lot, we’re not going to find much, if anything, wrong with it.”

Thompson says he always starts out his vehicle inspections by climbing into the cab and looking around. “You can tell a lot about how the truck was maintained just from a quick cab inspection,” he says.

Start by noting the general condition of the cab. See if the seats are ripped, and look for any broken glass on gauges and windows. Make sure all the switches are in good working order and that nothing is loose or broken. Note the transmission type and check to see if the rig has an exhaust brake. Also verify that the PTO controls are in good working order.

Front-end inspection should target engine
Move to the front of the truck and pull the hood open. You’ll have full access to the engine compartment and you’ll be able to inspect the front suspension. Engine checks are pretty straightforward. Be alert for any signs of oil leaks around the engine, particularly around the valve cover gasket. It’s also a good idea to shine a flashlight on the bottom of the engine and oil pan to see if leaked engine oil is present.

Look over the radiator and make sure it’s leak-free as well. The cooling fins should be clear of debris and all the hoses need to be in good condition. If the engine is cool, go ahead and crack the radiator cap and assess the condition of the engine coolant. Be especially alert for any signs of rust or oil in coolant.

Next, look over the engine’s drive belts and all visible wiring harnesses. Check the engine oil and transmission fluid (if the truck has an automatic). Later, when you’re test-driving the truck, reopen the hood and remove the oil filler cap. You’re looking for blowby, which is when oil gets past the piston rings and is burned in the combustion chambers. If you see smoke (or in a worst case scenario, oil spray) shooting out of the filler neck, the engine is probably going to need a ring job in the near future.

With the hood up, you should have good lines of sight to the front suspension, particularly the kingpins. Look the suspension over for damage or obvious signs of misalignment, but know that you won’t be able to tell much about the suspension just from a visual inspection. Thompson says your main inspection point should be the tires. “The tires will tell you a lot about the condition of both the front and rear suspension,” he says. “If they’re irregularly worn, or one side has markedly smoother tread than the other, it’s a good bet the front suspension will have to be adjusted or repaired.”

Dump body inspection
At the rear of the truck, take a moment to find out what type of rear suspension is on the vehicle. Make certain the suspension is up to the job at hand. Our sample rig was equipped with a Mack Camelback heavy-duty suspension. But some air suspensions are designed for on-highway applications and won’t hold up well in off-road work.
Also look for obvious damage and check the condition of the rear tires to make sure they’re evenly worn. You should also take a minute to get down and check the rear axle and differential. Again, severe damage is your main concern, although you should verify that the differential is not leaking gear oil.

Now you’re ready to inspect the truck’s dump body. First off, check the condition of the floor. Look for any signs of washboarding, or waves, in the floor. “Washboarding tells you the truck has been hauling rip rap or other potentially damaging materials or it’s been overloaded,” Thompson says. “It’s not a red flag, but certainly bears further investigation, depending on the age of the truck. In a worse case scenario, the integrity of the floor could be severely damaged.”

Walk around the sides of the dump body and look for any cracked weld lines or other types of serious damage. At the rear of the body, Thompson says to be sure and check the bed’s lift hinge on both sides of the truck. “This hinge point bears all the weight when you’re dumping a load,” he says. “Make absolutely certain that the hinge is in good condition and there is no excessive play present in the hinge assembly.” Finally, examine the tailgate, particularly the locking pins at its base. You want to make sure the tailgate and the locking pins are correctly lined up with the sides and floor of the body.

Raise the bed, run the truck
Now you’re ready to start the truck. But before you take it for a test drive, raise the dump body to its fully height, set the safety bars in place, and spend a few minutes looking over the frame, body bottom and power train for damage or abuse. The lift cylinder should also be inspected for hydraulic leaks and damaged areas. Pay special attention to the rod and make sure its not scarred or pitted.

Back in the cab, make sure the oil and air pressure and all other gauges are in the green and there’s proper tension on the clutch pedal. Beyond that, listen for any unusual noises and take note of the truck’s power curve and acceleration. One good thing about trucks, Thompson says, is that they aren’t good at hiding mechanical problems. “If there’s any trouble, odds are you’ll find it during the test drive,” he says.