Abstract: A hydraulically-actuated multi-step transmission is adapted to prevent the occurrence of engagement shocks of a direct-coupled or lock-up clutch associated with a torque converter. Downshifting is carried out once with the direct-coupled clutch (8) engaged when the vehicle is slowed toward a stop. This is followed by a further downshift with the accelerator released and the direct-coupled clutch disengaged.

Abstract: A method of automatically changing the speed of a self-propelled motor vehicle while supplying an adequate amount of cooling oil to a retarder during retarder operation, avoids unnecessary shifting even under conditions wherein an accelerator is released. The method of automatic speed change is so adapted as to move the shift points at each stage of speed to a higher vehicle-speed side as compared with normal driving.

Abstract: A method for automatically changing the speed of a dump truck for use as a construction vehicle which is capable of improving the fuel cost by utilizing the engine output effectively and efficiently, improving the durability of the power transmission system and giving the driver a comfortable ride. According to this automatic speed change method, a desired, optimum speed stage which meets the loading condition of the dump truck and/or the engine output condition can be selected by using controllers each having a built-in computer.

Abstract: A method for automatically changing the speed of a dump truck for use as a construction vehicle which is capable of improving the fuel cost by utilizing the engine output effectively and efficiently, improving the durability of the power transmission system and giving the driver a comfortable ride. According to this automatic speed change method, a desired, optimum speed stage which meets the loading condition of the dump truck and/or the engine output condition can be selected by using controllers each having a built-in computer.

Abstract: An object of this invention consists in exactly specifically identifying the position where abnormality arises in a speed changing system installed on a construction machine or similar vehicle. Specifically, a microprocessor (29) determines whether or not clutches H and L and clutch R, 1st, 2nd, 3rd and 4th are brought in an engaged state in conformity with clutch pressure commands (C.sub.1 l to C.sub.7). In addition, the microprocessor (29) determines whether or not the clutches are selected and then brought in an engaged state in conformity with the clutch pressure commands and shafts (2a, 7a and 8a) located before and behind the clutches are rotated in conformity with speed reduction ratios corresponding to the selected clutches. Thereafter, the microprocessor (29) exactly specifically identifies based on the results derived from the aforementioned determinations the position where a failure arises in the speed changing system.

Abstract: A brake system for a construction vehicle which ensures the safety of the vehicle when it is parked on a sloping road and started again, and enables the vehicle to get away for itself from a dangerous place where it has been brought to an emergency stop. It includes a battery relay which is closed if a main switch is turned on, a parking brake switch provided with a self-holding relay, an emergency brake switch and a solenoid valve for a parking brake. The parking brake switch, emergency brake switch and solenoid valve are connected in series to a power source via the battery relay one after another.

Abstract: A controller device for a wheeled construction machine has a variable speed lever for electrically controlling steps of speed of a transmission disposed near a steering wheel. It comprises a combination switch box disposed at the top of a steering column, a variable speed lever of a length enough for the leading end thereof to protrude slightly from the periphery of the steering wheel disposed on the left side of the combination switch box in such a manner as to approximate the steering wheel, and a control lever for turning on and off various lamps disposed protrudingly on the right side of the combination switch box. At least either of the variable speed lever and the control lever is attached to the combination switch box.