The 45RFE is a new generation electronically controlled rear wheel drive transmission. It employs real-time feedback, closed-loop modulation of shift functions to achieve excellence in shift quality and to meet severe durability goals. The 45RFE uses no shift valves; all friction element applications are effected with high-flow electro-hydraulic solenoid valves. A unique gear train arrangement of three planetary carriers allows all sun and annulus gears to have identical numbers of teeth and to use common pinion gears in all carriers. This results in substantial manufacturing simplification. The three-planetary system is designed for four forward ratios of 3.00, 1.67, 1.00 and 0.75 and one reverse gear ratio equal to the low gear ratio. A fifth ratio of 1.50 is used mainly in certain kick-down shift sequences for highway passing. A sixth forward ratio, an additional overdrive ratio of 0.67, is available in the hardware. A unique valve body arrangement allows for two manually selectable forward gears and one reverse gear in power-off operation. Torque-based line pressure control and a two-stage pump with independent lubrication feed are provided for improved efficiency and cooling.
A 150,000 mile (241,400 km) truck customer with moderately high engine torque and power requirements was chosen as the design endurance target for this transmission. Early simultaneous engineering, conducted with the transmission, casting, electronic, torque converter, assembly, and supplier groups was a key factor for a successful development program and a remarkable launch in an all-new plant where a “green field” existed only a short time before. A significant contribution to this success is attributable to the entire design being done in electronic files.