Fix it right the first time.
Practical diagnosis and maintenance guides for heavy-duty trucks and trailers — written for the people who turn the wrenches. New guide every day.
Using PartsNow
Step-by-step help for the website and the mobile app.
Using PartsNowHow to Find the Right Truck Part on PartsNow.ai
Search 50,000+ heavy-duty truck and trailer parts by part number, VIN, photo — or just describe what you need in plain words. Here's how.
Using PartsNowHow to Order on PartsNow: Shipping or Free Knoxville Pickup
From cart to checkout on partsnow.ai: nationwide shipping with real-time UPS/USPS/FedEx rates, or free pickup in Knoxville, TN — ready in 1-2 business days.
Using PartsNowHow to Use the PartsNow AI Assistant (Chat, Photo & VIN)
PartsNow's AI assistant finds parts, checks compatibility and crosses part numbers — by chat, photo or VIN. Here's how to get the most out of it.
Using PartsNowGetting Started With the PartsNow App (iOS & Android)
Download the PartsNow app for live video help from Mike, photo part scanning, catalog search and checkout — truck parts from the driver's seat.
Using PartsNowMike Live: Show Your Truck Problem on Video, Get the Part
In the PartsNow app, Mike Live opens a video session — point your camera at the part or problem and Mike identifies it and finds what you need.
Using PartsNowHow to Identify a Truck Part From a Photo (Web & App)
Got the old part in your hand but no number on it? Upload a photo on partsnow.ai or scan it in the app — the AI identifies it and finds matches.
Repair & maintenance
A new guide every day, grounded in real field manuals.
Electrical & LightingTrailer ABS Light Won't Go Off? Sensor & Wiring Guide
Trailer ABS light staying on? Step-by-step diagnosis for wheel speed sensors, harness corrosion, and ECU faults before you swap parts.
Aftertreatment & EmissionsDEF Lines Freezing? Winter Prevention & Fixes for Fleets
Stop DEF freezing from parking your trucks. Learn heated-line checks, tank insulation, and SCR fault codes before derates hit.
Trailer & CouplingFifth Wheel Not Locking? Diagnosis & Fix Before It Fails
Fifth wheel not locking or slipping under load? Step-by-step diagnosis, lube checks, jaw inspection, and rebuild-vs-replace guidance.
Brakes & Wheel EndGrease vs. Oil-Bath Hubs: Picking the Right Wheel End Lube
Grease vs oil-bath wheel end lube compared: intervals, seal compatibility, and failure signs to help you pick right for your fleet.
Air SystemAir Dryer Not Purging? Diagnose Wet Tanks Fast
Air dryer not purging? Diagnose wet tanks fast with checks for governor, purge valve, heater, and cartridge on trucks like Kenworth T800.
