A controller-assisted, manually shifted compound transmission system (10) and range shift control method therefor. Range section (16B) shifts are normally automatically implemented by a range shifter (28) under commands (56) from a controller (54) in response to manual initiation. Under certain operating conditions ((ES_MIN < OS*GR) and (ES_MAX < OS*GR_CLR)) automatic range downshifts without driver initiation are commanded.

A control method/system for controlling range section (14) shifting in a range-type transmission (10) having a "repeat-H" (200) or "double-H" (202) shift mechanism. Under certain conditions, a shift into an operator-selected target ratio (GR_T) is unacceptable and a shift into an alternate ratio (GR_ALT) is implemented. The alternate ratio is a ratio available at an operator-selected main transmission position (1/5, 2/6, 3/7, 4/8) with the range section in a range ratio not selected by the operator.

A shift control system is provided for an automatic transmission in which a secondary shifting unit capable of being shifted to a high speed stage or a low speed stage and a primary shifting unit capable of setting one of plural speed stages including a reverse speed stage are connected in series and the secondary shifting unit can be set to the high speed stage upon setting the reverse speed stage. The shift control system is equipped with a reverse range detector for detecting a shift from a neutral range to a reverse range, a vehicle stop detector for detecting a vehicle in a stopped state, and a high speed stage command device for setting the secondary shifting unit at the high speed stage when subsequent to setting of the primary shifting unit at the reverse speed stage as a result of a shift to the reverse range, the vehicle is determined by a signal from the vehicle stop detector to have substantially stopped.

A powershift transmission having input, center and output clutch sections (70, 75, 80), each section including a plurality of clutches, is arranged to have a high and a low range (L, H) of input/output speed ratios with some of the lower ratios of the high range (H) being substantially equal to some of the higher ratios of the low range (L). During upshifting the shift sequence is 1L, 2L,....(N-2)L, (N-1)L, NL, 3H, 4H, ...NH and during downshifting the sequence is NH, (N-1)H... 2H, 1H, (N-2)L....2L, 1L wherein ratios (N-1)L and NL are substantially equal to 1H and 2H, respectively, L represents the low range, H represents the high range and N represents the number of gear ratios within each range. The arrangement avoids the need for simultaneous clutch swaps in all three clutch sections and reduces the number of shifts requiring simultaneous clutch swaps in the center and output clutch sections (75, 80). This reduces the load placed on an engine during shifting because of the inertia of moving parts in the transmission, thereby providing smoother shifting particularly under heavy load conditions.

A method and apparatus for controlling a power transmitting system for an automotive vehicle, including a continuously variable transmission (CVT) and an auxiliary transmission which is connected to the CVT and which is automatically shifted from one of two or more forward drive positions to the other depending upon operating conditions of the vehicle. To control the speed ratio of the CVT, a target speed of the input shaft of the CVT is determined according to one of different relationships between the target speed and at least one variable such as a currently required output of the engine. The relationships are stored in memory, corresponding to the forward drive positions of the auxiliary transmission. The appropriate relationship is selected depending upon the forward drive position in which the auxiliary transmission is currently placed while the transmission shift lever is in an auto-shift or engine-brake position. The automatic shift-down and shift-up operations of the auxiliary transmission may be effected according to predetermined shift patterns corresponding to drivability modes of the vehicle selected on a suitable drivability selector device.

A method and apparatus for controlling a power transmitting system for an automotive vehicle, including a continuously variable transmission (CVT) and an auxiliary transmission which is connected to the CVT and which is automatically shifted from one of two or more forward drive positions to the other depending upon operating conditions of the vehicle. To control the speed ratio of the CVT, a target speed of the input shaft of the CVT is determined according to one of different relationships between the target speed and at least one variable such as a currently required output of the engine. The relationships are stored in memory, corresponding to the forward drive positions of the auxiliary transmission. The appropriate relationship is selected depending upon the forward drive position in which the auxiliary transmission is currently placed while the transmission shift lever is in an auto-shift or engine-brake position. The automatic shift-down and shift-up operations of the auxiliary transmission may be effected according to predetermined shift patterns corresponding to drivability modes of the vehicle selected on a suitable drivability selector device.

A transmission controller determines that a select operation has been performed from a reverse range to a drive range if a time during which a range other than the drive range has been selected is longer than a predetermined time threshold value and an input rotation speed of a transmission is lower than a predetermined rotation speed threshold value and determines that the select operation has been performed from a parking range or a neutral range to the drive range if the time during which the range other than the drive range has been selected is shorter than the time threshold value or the input rotation speed is higher than the rotation speed threshold value when the select operation has been performed from the range other than the drive range to the drive range during vehicle stop.