Buying a used semi truck checklist: pass, ask or walk away

This checklist is built to use standing next to the truck. Mark each item pass, ask or walk away; the condition scale at the bottom adds it up, and you can print a blank copy to take along. It works for any used truck, from a 26 ft box truck to a heavy-haul tractor, with a few items that apply only to tractors.

The checklist

Paperwork first

Do the paperwork before you drive anywhere. Ask the seller for a photo of the title and the VIN plate. Check that the name on the title matches the seller and that there is no salvage or rebuilt brand. Run a lien check: the title shows recorded lienholders, your state motor vehicle agency can confirm the record, and for business-owned trucks a UCC search at the secretary of state can reveal liens filed against the company's equipment. Decode the VIN with the semi truck VIN decoder and compare the result with the listing.

Mileage and the odometer

Federal odometer disclosure rules in 49 CFR Part 580 exempt vehicles with a gross vehicle weight rating over 16,000 pounds, so most semi trucks change hands without a federal odometer statement. That makes other evidence important: the ECM's recorded miles and hours, dated service records, oil analysis history and wear on the seat, pedals and steering wheel. If they disagree, believe the records and the ECM over the dash.

Engine: ECM download and oil analysis

An ECM download shows engine hours, idle time, fault codes and how hard the truck was driven. An oil analysis can reveal coolant or fuel in the oil and unusual wear metals that point to problems inside the engine. Ask a heavy truck shop to do both. Sellers who refuse are telling you something.

Aftertreatment and emissions

Check that the diesel particulate filter, SCR system, DEF system and sensors are present and original, and that there are no active emissions faults. Removing or disabling emissions equipment is illegal under the Clean Air Act and can make a truck hard to register, insure, finance or sell. If the truck will run in California, check its Clean Truck Check status with the CARB compliance checker.

Drivetrain, frame and suspension

Drive the truck loaded if you can. Shifts should be clean, the clutch or automated transmission should not slip, and axles should be quiet. Under the truck, look along the frame for cracks, bends, rust-through and fresh welds, especially near the fifth wheel and rear axles. New undercoating over one area can hide a repair. Check air bags, shocks and suspension mounts.

Tires and brakes

Measure tread depth across every axle and look for uneven wear, which can point to alignment or suspension problems. Read the four-digit date codes on the tire sidewalls. Check brake linings, drums or rotors and slack adjusters, and make sure the air system builds pressure and holds it.

Cab and body

Wear on the seat, pedals and wheel should fit the miles. Test every gauge, light, heater and air conditioner. Look for water stains and mold. For box trucks, check the floor, doors, seals and liftgate; for flatbeds, the deck boards and tie-down points.

Questions to ask the seller

• Why are you selling the truck, and how long have you owned it?
• What work did it do: long haul, regional, local, heavy loads?
• When were the last major repairs, and do you have the invoices?
• Has the engine been rebuilt or overhauled, and at what miles?
• Has the emissions system been cleaned or replaced, and is every part original?
• Is there a loan on the truck, and how will it be paid off at closing?
• Can my mechanic inspect it and download the ECM before I decide?

Write the answers down and compare them with the records. Vague or changing answers are a warning sign.

What to bring to the inspection

A flashlight, a tire tread gauge, gloves, your phone for photos of the VIN plate, odometer, title and any damage, and this checklist, printed. If you can, bring a mechanic or arrange for the truck to go to a shop. Ask to start the engine cold, so the seller has not warmed it up to hide starting problems.

Reading the condition scale

The scale counts pass items as one point and ask items as half, out of the items you have marked. Eight or more out of ten usually means a candidate worth a professional inspection and a negotiation over the ask items. Lower scores mean every ask item needs a price before you make an offer. Any walk-away item overrides the score.

Checking a box truck or hotshot

The same checklist works for smaller rigs, with a few changes. For a 26 ft box truck, look closely at the box floor, roof, door rollers and liftgate, and confirm the GVWR on the door label matches the work you plan; we only dispatch box trucks 26 ft and up. For a hotshot pickup and trailer, check the hitch, the trailer's deck and axles, and the truck's transmission and cooling system, which work hard under heavy loads.

After the checklist

If the truck passes, pay an independent shop for a pre-purchase inspection, then negotiate using written repair quotes for any ask items. Read the used semi truck buying guide for negotiating and closing, used semi truck financing for the loan, and what to do after buying a semi truck for the first weeks. Set up a repair reserve with the maintenance reserve calculator, and if you are still deciding whether to buy at all, read is buying a semi truck a good investment.

General information about buying, not financial, tax or legal advice. RigCaptain is not a lender, broker, dealer or insurer. Read every contract and ask a tax professional or attorney about your own deal.