2021 Kenworth T680

Duty cycle profile, 398,350 miles suggests steady highway time with typical long-haul wear points, cooling stack cleanliness, aftertreatment health, and driveline lash become the telltales. Service history matters more than cosmetics at this mileage, especially for DPF performance, DEF dosing consistency, and any active or parked regen frequency changes. Powertrain details, engine, transmission, and axle ratio are not provided, so the evaluation centers on verification steps. ECM pull is the first stop, confirm total miles, idle percentage, cruise usage, fault history, derate events, regen counts, and any repeated NOx, EGR, or DEF related codes. Road test should check for smooth torque delivery, shift quality under load, engine brake response, and any vibration through the seat or steering that points to U-joints, carrier bearing, or tire balance issues. Frame rails and crossmembers should be checked for straightness, corrosion at fastener points, and any added holes or repairs around suspension hangers. Fifth wheel and slide rails need inspection for jaw wear, top plate scoring, and slider lock engagement, plus air line routing and gladhand condition for chafe. Steer axle and front end should be checked for kingpin play, tie rod end looseness, air bag condition, and uneven tire wear that hints at alignment or bushing wear. Cab interior and sleeper condition give clues about operator care, look for pedal wear versus stated miles, seat base play, HVAC performance, and dash warning lamps at key-on. Electrical and air systems should be verified for build time, air loss rate, compressor cycling, and any evidence of harness rub-through near the firewall and frame. Identification points, VIN 1XKYD49X0MJ468104 and stock 0635253 should be matched across cab tag, frame stamp, and paperwork before final acceptance.