What is a key consequence of not performing rev matching during a downshift?

When downshifting in a manual transmission vehicle, rev matching involves increasing the engine RPM to match the speed of the wheels that are now turning faster as a result of the downshift. Failing to perform this technique can lead to drivetrain shock, which is the sudden and harsh jolt felt throughout the vehicle when the engine speed does not align with the speed of the wheels. This occurs because the engine is forced to adjust suddenly to the difference in RPMs, which can put excessive strain on the driveline components and lead to mechanical wear over time.

Additionally, not rev matching can result in less control over the vehicle during the downshift process, making it harder to maintain stability and traction, particularly in slippery conditions. This is because the abrupt change in engine speed can lead to wheel lock-up or a loss of traction. Understanding the effect of rev matching is crucial for smoother driving and better vehicle handling, as it prevents unnecessary stress on the drivetrain and contributes to overall driving comfort.