Understanding Shift Flare: Causes, Symptoms, and How to Avoid Them

Shift flare refers to an unwanted and temporary increase in engine RPM during a gear shift. While this phenomenon is more commonly associated with automatic transmissions, it can also occur in manual transmissions under certain conditions. Let's delve into the details of shift flare, its causes, symptoms, and how to avoid this issue in both types of transmissions.

What is Shift Flare?

Shift flare occurs in automatic transmissions when the engine RPM momentarily increases as the transmission shifts gears rather than smoothly transition to the next gear. This phenomenon can be observed when the shift from one gear to another does not allow the engine speed to drop appropriately, resulting in a brief spike in RPM before the new gear engages.

Shift Flare in Automatic Transmissions

Automatic transmissions are equipped with various internal clutches that connect different parts of the driveline. When a gear shift occurs, one clutch is disengaged while another is engaged, changing the gear ratio. If this process is done smoothly, torque is transferred seamlessly, and the engine speed adjusts accordingly.

However, if the parameters such as clutch engagement rate, pressure, or timing are off due to internal clutch or band failures, a poor shift occurs. In this scenario, the resultant shift flare can be observed. The releasing clutch might disengage too quickly, or the engaging clutch might not apply sufficient pressure, causing the transmission to slip during the shift. Consequently, the engine speed spikes before settling into the new gear.

Shift Flare in Manual Transmissions

While manual transmissions provide greater control to the driver, they are less prone to shift flare without technical issues or driver errors. Drivers can influence the shift feel of a manual transmission by using the clutch and gears properly. However, similar symptoms to shift flare can occur if the driver shifts too quickly or if there is an issue with the clutch. Poor clutch engagement or disengagement can lead to a rough or jerky shift, which may result in a sudden increase in RPM.

Causes and Symptoms of Shift Flare

For Automatic Transmissions:

Internal clutch or band failure Incorrect timing or pressure when engaging or disengaging clutches Drifting in throttle position when shifting gears

For Manual Transmissions:

Improper clutch engagement or disengagement Driver errors in shifting technique

The key symptoms of shift flare include:

A sudden increase in engine RPM during a gear shift A rough or jerky shift feel Uneven torque transfer

Preventing Shift Flare

In Automatic Transmissions:

Regular maintenance, including fluid changes and clutch inspections Ensuring proper engine tuning and calibration Using high-quality transmission fluid and filters

In Manual Transmissions:

Improving driving technique and clutch control Gradually applying the clutch and engaging gears Avoiding lever or gear changes while the throttle is set

Conclusion

Shift flare can be a frustrating issue for both automatic and manual transmission owners. Understanding the causes of shift flare and taking proactive steps to prevent it can significantly improve the performance and longevity of your transmission. Whether you need to address clutch failures, internal band issues, or simply improve your shifting technique, regular maintenance and attentiveness to your vehicle's operation are crucial.