Drivetrain Lash

📖 YOUCANIC Automotive Glossary

Drivetrain lash (also called driveline lash, backlash, or driveline play) is the total accumulated mechanical play in all the rotating components between the engine’s flywheel and the driven wheels — including the transmission gears, torque converter, driveshaft U-joints or CV joints, differential ring and pinion gears, and axle shafts. Every gear mesh and universal joint has some designed-in clearance, and the cumulative effect is felt as a clunk or thud when transitioning between acceleration and deceleration or vice versa. Some drivetrain lash is normal and expected; excessive lash indicates worn components that need attention.

Excessive drivetrain lash manifests as a noticeable clunk when shifting from park to drive or reverse, a thud when lifting off or reapplying the throttle during driving, and a rhythmic clicking or ticking during slow parking lot maneuvers. Common causes of increased lash include worn U-joints (check for play by hand — any movement means replacement), worn differential ring and pinion (requires differential service), worn CV joints (clicking during turns), loose or worn transmission output shaft components, and worn engine or transmission mounts that allow excessive powertrain movement amplifying the lash sensation.