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Heavy Trucks

Class 8 Semi Tractor Pre-Purchase Inspection Checklist

A guided, do-it-yourself pre-purchase inspection checklist for used Class 8 semi tractors, sleeper or day cab: Freightliner, Kenworth, Peterbilt, Volvo, International, Mack and Western Star, with Detroit, Cummins, PACCAR, Volvo and Mack engines. No mechanic needed: each check tells you what to look for and what counts as a fail, from records, idle hours and emissions to air brake tests, fifth wheel, engine, aftertreatment, transmission, tires and the sleeper or day cab, plus a road test.

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90 days of access. Inspect and compare up to 12 items of this type.

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What you get

  • No mechanic needed. Most checks need only your eyes, a flashlight and a tire gauge; a few optional deeper checks go further if you have the tools or bring in a mechanic.
  • A guided checklist written for this kind of purchase: every question says what to look for and what counts as a fail. Ready to use the moment you pay.
  • Inspect on your phone: answers save as you go, with photos and notes on any question.
  • Send it to a mechanic, supervisor, colleague, or employee by text or email. They need no account.
  • A report that puts the problems first, with photos, times and location.
  • Inspect and compare up to 12 vehicles, machines or trailers of the same type with one purchase, side by side, before you decide.

Known problems, checked

Comes with a guide to the known problems and red flags to watch for.

How it works

  1. Choose a checklistPick the one that matches what you are buying, and pay by card. No account to set up first.
  2. Add what you are inspectingEnter the item, the asking price and where it is. Add as many as you are considering.
  3. Inspect it, or send itWork through the checklist on your phone, or send it to a mechanic, supervisor, colleague, or employee to do for you.
  4. Read the report and compareSee the problems first, with photos. Put your options side by side and decide.

What it covers 83 questions

  • Records and Identity9 questions
  • Frame, Cab and Fifth Wheel7 questions
  • Engine and Exhaust12 questions
  • Air Brakes8 questions
  • Steering, Suspension and Wheel Ends7 questions
  • Tires4 questions
  • Transmission and Drivetrain6 questions
  • Electrical, Cab and Controls8 questions
  • Sleeper Cab6 questions
  • Day Cab3 questions
  • Road Test5 questions
  • Freightliner and Western Star Only2 questions
  • Kenworth and Peterbilt Only2 questions
  • Volvo and Mack Only2 questions
  • International Only1 question
  • Final Review1 question

A sample of the questions

  • VIN, title and liens
  • Frame rails and crossmembers
  • Engine oil
  • Air pressure build-up
  • Steering free play
  • Steer tires
  • Clutch (manual transmissions)
  • Gauges and warning lights

This is a sample. The full checklist is yours when you buy.

Before You Start

You don't need a mechanic or to be one to conduct this inspection. Most questions need only your eyes, a flashlight and a few low-cost tools, and each one tells you exactly what to do and what counts as a fail.

You do need a driver with a Class A CDL for the road test, and you should hold one yourself to drive it home.

Allow about three hours, including the air brake tests and a road test of at least 20 minutes.

For Class 8 semi tractors, sleeper or day cab, diesel: Freightliner Cascadia and Coronado, Kenworth T680, T880 and W900, Peterbilt 579, 567 and 389, Volvo VNL, International LT and LoneStar, Mack Anthem and Pinnacle, Western Star and similar. Answer the Sleeper Cab section on a sleeper and the Day Cab section on a day cab. Not for trailers, or for electric, natural gas or hydrogen tractors.

Before you go, ask the seller to:

  • Leave the engine cold and the air tanks low. Some checks need a cold start and a full air build-up.
  • Have the title, keys, service records and the last annual (DOT) inspection report ready.
  • Park the tractor on firm, level ground with room to walk all the way around it and to drive it.
  • Have a trailer available, if possible, for the coupled test.
  • Agree a road-test route and who will drive.

Go in daylight, with the wheels blocked. Never get under the tractor while it is held up only by its air suspension or a jack: use stands rated for it. Stay clear of the fifth wheel, the driveshafts and the fan while the engine runs.

Answer every question as indicated. Skip the sections for a cab type, equipment or a make the tractor does not have (answer Not applicable).

Questions marked "Deeper check" are optional extras that need special tools. Skip any you can't do, or ask a mechanic to do them.

Write readings in the note, and add a photo of anything that fails.

Bring:

  • A flashlight
  • A tape measure and a watch or phone timer
  • A tread depth gauge and a tire pressure gauge with a dual-wheel head
  • A basic multimeter, for the batteries and charging voltage
  • A heavy-duty code reader for the round 9-pin port (or ask the seller to show codes on the dash)
  • A 7-way trailer plug tester
  • Wheel chocks
  • Gloves and paper towels
Tools for a Deeper Inspection (Optional)

You don't need any of these to use this checklist. For the questions marked "Deeper check", or if you bring in a mechanic, these are the tools needed, as well as those in Before You Start:

  • A ruler marked in sixteenths of an inch, for brake pushrod travel
  • A heavy-duty scan tool or the maker's software for this engine and transmission (for example Detroit DiagnosticLink, Cummins INSITE, PACCAR MX Access, Volvo Tech Tool), for idle time, fault history and DPF data
  • A floor jack or bottle jack rated for the front axle, and stands, for the kingpin and wheel bearing check
  • The fifth wheel maker's lock gauge, for the lock adjustment
  • Oil and coolant sample bottles and a lab, for an oil analysis
  • A cooling system pressure tester with adapters for this engine
Sources and Standards
  • FieldDone pre-purchase inspection protocol for Class 8 semi tractors (October 2026)
  • Your tractor's own operator's manual and service information, and the engine, transmission and fifth wheel makers' manuals, matched to the VIN and serial numbers
  • US Federal Motor Carrier Safety Regulations, annual inspection standards (49 CFR Part 396, Appendix A)
  • Commercial Vehicle Safety Alliance, Operation Airbrake inspection procedure
  • Commercial driver's licence manual (your state or province), air brake inspection section
  • NHTSA recall lookup
  • Kenworth T680 operator's manual
  • SAF-Holland fifth wheel manuals
  • PACCAR MX Access
  • Cummins INSITE support
  • Eaton Cummins transmission manuals and driver instructions