How are shift points determined in an automatic transmission?
How are shift points determined in an automatic transmission?
In an automatic transmission, predefined points determine when the transmission will shift up (higher gear number, faster speed, lower gear ratio) or down. Generally, transmission shift points are easy to read and are often known but in some cases, they are not.
Is there a third rule for shift point tuning?
The third rule is needed to avoid the case where a vehicle shifts up, the RPM is reduced in the new gear, then the vehicle shifts back down, starting an infinite cycle of up and downshifting. It is simple to check whether there is enough space between up and downshifting points using a simple relation between the RPM before and after a shift:
What’s the WOT shift point 56 at wide open throttle?
WOT Shift Point 56 – A MPH command for the 5-6 up-shift at Wide Open Throttle Shift Pressure 12 – Percentage based increase in shift pressure of the transmission for the 1-2 shift Shift Pressure 23 – Percentage based increase in shift pressure of the transmission for the 2-3 shift
When do you use the quick shift point?
Many vehicles have two sets of up and downshift points, one (“normal”) that is active at most throttle positions, another higher set (often called “quick shift”) used when the throttle is near 100%. The quick shift is used under hard acceleration to help the vehicle stay in a higher RPM range, where the engine generally has more power.
Is it possible to read transmission shift points?
Generally, transmission shift points are easy to read and are often known but in some cases, they are not. It is nevertheless important to confirm that these shifting points are internally consistent. There are three rules to consider about tuning shifting points: Shift up below the maximum RPM.
The third rule is needed to avoid the case where a vehicle shifts up, the RPM is reduced in the new gear, then the vehicle shifts back down, starting an infinite cycle of up and downshifting. It is simple to check whether there is enough space between up and downshifting points using a simple relation between the RPM before and after a shift:
What causes a car to shift to the up shift point?
Once in the lower gear, the vehicle might have enough torque to accelerate to the up-shift point, causing the transmission to shift back into the higher gear again. This is normal behavior and there is no way to completely avoid it in a vehicle that shifts automatically.
How to reset adaptive shifting points on Mercedes Benz?
This procedure will reset the adaptive shifting points in your Mercedes-Benz automatic Transmission Control Unit (TCU). These simple do it yourself instructions take less than 5 minutes. No tools are required to perform this procedure and make your Mercedes-Benz shift like new. Try this if your car has been shifting sluggish recently.
