Understanding Shift Feel and Quality
There are different strategies and devices used in todays automatic transmission to improve shift feel. Just as one device such as a band is being released another device (Clutch Pack) is being applied. This shift timing is vital for smooth shifting.
Devices like the accumulator, restricting orifice, and chack ball are used to provide smooth shifting. To improve an automatic transmissions shift feel a band is applied just as the clutch pack is being released. The timing between these must be exact or the vehicle will suffer harsh shifting and slippage. The friction devices will prematurely wear leaving debris in the sump.
The accumulator is a spring loaded piston inside a bore located in a clutch or band circuit. It absorbs the pressure buildup by diverting some of the systems pressure from the apply piston to the pocket created by the piston as it compresses the spring. When this device malfunctions (usually a broken spring) the vehicle will shudder and suffer from harsh shifting.
Restricting orifice and check balls simply restrict the flow of pressure controlling the amount of fluid that can flow through at any given time. Electronic solenoids are controlled by the TCM (transmission control module) and electronically pulse or cycle to control the amount of fluid in the control circuit.
A bad electronic shift solenoid would typically initiate a code somewhere in the p0700 range. All of these devices and methods are dependant on vehicle speed, load, and the intentions of the driver. They are used in different applications to improve a transmissions shift quality and feel.
