Transmission Control Systems: Description and Operation

FUNCTIONS OF TRANSMISSION CONTROL COMPUTER
The transmission control computer, installed at lower left of the instrument panel, determines the speed change point and lock-up point of the transmission as well as speed change range of transfer by receiving signals from each sensor, and sends signals to each solenoid for control.
In addition, it contains a diagnosis function and fail-safe function.

OPERATION OF TRANSMISSION CONTROL COMPUTER





Speed change and lock-up pattern
If you select a speed range and a lock-up pattern as shown by specifying respective positions of transmission shift lever, transfer shift lever and pattern select switch, the transmission control computer controls speed change and lock-up operations based on the specified pattern in accordance with the degree of throttle opening and vehicle speed.





Overdrive and lock-up operating conditions
The overdrive and lock-up clutch operate if the conditions shown are satisfied.


TRANSFER HIGH-LOW SHIFT RANGE
The 30-8OLE transfer differs from previous manual transfers in that a shift into high or low range is possible while the vehicle is in motion. This function was not only created for shifting into all ranges (vehicle speed, throttle opening angle) but was made with the idea of improving shifting performance, transfer conditions and the prevention of engine overrun in mind.
Operation
This shifting possibility range is controlled by the ECT computer and when a high-low shift is done within this range, the ECT computer operates the No. 4 solenoid which carries out the high-low transfer shift. If a shift is attempted outside this range, the high-low shift will not take place until vehicle speed and throttle opening angle come within the range.
There are three shifting possibility ranges for when the transmission gear is in first second or third gear, matched to each transmission shift range (L, 2, D). Although in the 1st and 3rd shifting possibility range the high low shift takes place according to the respective gear position, in the 2nd gear shifting possibility range, when a transfer is made from 1st gear, only after the transmission has up-shifted into second will the high low shift take place.
Further, even though the 2nd range and D range high low shifting possibility range overlaps with the 1st and 2nd range, within this range the high low shift will take place for example, in the first gear range if the transmission is in the first gear, or in the second gear range if the transmission is in the second gear.