GUARD ASSEM. 4Y7221 - Caterpillar

Illustration 1 g01053300The fill calibration function is used in order to optimize the shift quality. This calibration procedure must be performed under the following conditions:
Perform the calibration before the machine is delivered to the customer.
Perform the calibration after replacing or servicing the ECM.
Perform the calibration after the moving of an ECM from one machine to another machine.
Perform the calibration after replacing or servicing any of the transmission solenoid valves.
Perform the calibration after replacing or servicing any of the transmission clutches, seals, pumps, etc.Two parameters are adjusted during the fill calibration, pulse time and hold level. The hold level is calibrated first. The pulse time is calibrated second. The fill calibration for each clutch is completed before the next clutch begins.During the fill calibration, the system software will detect the end of fill cycle for the clutch. The end of the fill cycle is detected by using a drop in converter output speed and a drop in the relative clutch (slip) speed. To effectively detect a drop in converter output speed, a load must be applied to the transmission. This can be accomplished by engaging one of the clutches that is not being calibrated. Hold Level CalibrationThe hold level calibration will determine the touch-up pressure that is applied to the clutch pack by the clutch piston. Each clutch command is pulsed and held at the minimum allowable hold level pressure for a specific duration of time. After a 2.0 second pause, the next clutch is pulsed, held, and released. This is repeated until all the clutches have been cycled. The hold level pressure is incremented and the cycle is repeated. The hold level pressure for a clutch is calibrated when the fill cycle is completed and the fill cycle is completed within the specified hold time. The corresponding hold level pressure is the calibrated value. After a clutch has been calibrated, the clutch is taken out of the cycle and a 3.0 second delay is inserted. The delay will allow the clutches that remain in the cycle to drain. This process continues until the hold level pressure reaches the maximum allowable value, or all of the clutches have been calibrated.A warning is displayed when the following conditions occur:
The hold level pressure for any single clutch exceeds the maximum value.
The hold level pressure is set at the minimum value and the clutch fills at a faster rate than the allowed cycle time.Pulse Time CalibrationThe fill time is calibrated by adjusting the pulse time. The ramp levels for each clutch are set to default values. Each clutch command is pulsed and each clutch command is ramped. Then, each clutch command is held to the hold level pressure that is calibrated. When the appropriate clutch is held, the hold level pressure is held until the end of fill is detected or 1.0 second has passed. The actual fill time is compared to the target fill time. The pulse time is increased or the pulse time is decreased in order to shorten the fill