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In 1994, the Kubota Corporation launched the Grand “L” Series of compact tractors to the worldwide market. SAE J1150 -TERMINOLOGY FOR AGRICULTURAL EQUIPMENT defines compact tractor as a small agricultural tractor equipped with a 540rpm rear PTO (SAE J1170) and a three-point hitch designed for Category I (SAE J715)implements only. These tractors generally weigh less than 1800kg, have less than 30 PTO kw, and are primarily designed and advertised for use with mowers and light-duty material handling equipment. The concept behind the development of this series of tractors comprises of 4 basic types with PTO power ranging from 18.7 to 27.6 kW (25 to 37 HP). It offers operator comfort, excellent dexterity, and high performance efficiency in a compact tractor configuration. The tractor performs well without any special skill by the operator. Further, it can utilize with equal efficiency such varied applications as light construction, grounds maintenance, and agriculture.

An electro-hydraulic control system was applied to a tractor and rotary tiller to provide automatic implement tilt control. The Automatic Implement Tilt Control (AITC) system maintains the rotary tiller horizontal or at a selected tilt angle independent of tractor rolling motion. The performance of AITC, especially accuracy and response time, has been found to be sufficient for the Japanese rice farming. As the leveling of soil surface has been substantial needs of farmers, AITC has resulted in rapid acceptance in Japan. Potential applications of AITC have been increased by locating all sensors on the tractor to make possible interchangeability between three-point hitch implements.

Normally, agricultural tractors require frequent shifting due to load changes or repetitive forward and reverse travel requirements. From the standpoint of maneuverability and workability, there is a strong demand for tractors with clutchless-transmission-operation similar to automobiles. However, power loss from the transmission is not desirable for heavy duty tractors, so should be eliminated as much as possible. To solve this problem, Kubota, Ltd. has developed the Glide Shift Transmission (GST) which employs a power synchro shift and single clutch pack system resulting in improved maneuverability and workability while obtaining a power efficiency equivalent to that of manual gear type transmissions. The GST has been applied to the L2550DT-GST (17.5 PTO kW) and L2850DT-GST (20.1 PTO kW) farm tractors. These tractors have been marketed since 1987. This report covers the design philosophy of the power synchro shift transmission and explains how it functions.