The frequencies, ratios, amplitudes and interpretations in this module are simplified fictional teaching data—not OEM limits or repair specifications. Road testing must be legal and safe, and any severe wheel, steering, suspension, structural or rapidly worsening vibration concern is a stop-work condition. Use the exact vehicle service information for inspection methods, runout, balance/force, bearing, driveline, alignment and repair specifications. Browser completion is not practical competency.
Turn subjective ride and vibration complaints into measurable evidence
12.1–12.5 built geometry, suspension, steering, wheel/tire and alignment knowledge. 12.6 combines them with rotational-frequency and condition-based diagnosis. Previous: 12.5 Wheel Alignment & Measurement. Next planned module: 12.7 · Chassis Service & ADAS-Related Alignment Considerations.
Classify the evidence before naming the source
Compare measured vibration to wheel, driveline and engine orders
This fictional model calculates candidate 1× frequencies. A match narrows the hypothesis; it does not prove the failed component.
Teaching equations: wheel RPM ≈ mph × 336 ÷ rolling diameter (in); wheel Hz = RPM ÷ 60; driveline Hz ≈ wheel Hz × final-drive ratio; engine 1× Hz = engine RPM ÷ 60. Real tire loaded radius, gearing, converter/clutch slip and drivetrain architecture can alter relationships.
Make the condition repeatable, then eliminate hypotheses
Ordered NVH/handling workflow
Complete the sequence in order.
Evidence
Best supported conclusion / next step
10-question knowledge check
Online NVH reasoning is not hands-on diagnostic competency
Use approved tools, safe road-test/test-stand conditions and exact service procedures. Observe the learner reproducing, measuring, isolating and verifying the complaint.
Student: ____________________ Date: __________ Instructor: ____________________