Patent ID: 8565985

Claim:
A transmission control device of a work vehicle composed of an engine, a travel device and a power transmission unit, the power transmission unit including a torque converter, a lock-up clutch and a transmission, the power transmission unit being configured to transmit an output of the engine to the travel device via either the torque converter or the lock-up clutch, and subsequently via the transmission, the transmission control device being configured to shift a high-speed gear of the transmission down to a low-speed gear in accordance with reduction in a vehicle speed, the transmission control device comprising: a load increase rate computation portion configured to compute an increase rate of a load acting on the work vehicle; and a transmission control portion configured to selectively shift the high-speed gear in a torque converter state, in which the lock-up clutch is disengaged, down to the low-speed gear in the torque converter state via the low-speed gear in a lock-up state, in which the lock-up clutch is engaged, when the load increase rate is less than a load increase rate threshold in shifting the high-speed gear down to the low-speed gear, and shift the high-speed gear in the torque converter state down to the low-speed gear in the torque converter state while skipping the low-speed gear in the lock-up state when the load increase rate is equal to or greater than the load increase rate threshold in shifting the high-speed gear down to the low-speed gear.