Multiple ratio transmission with swap-shift controls

An automatic transmission for a vehicle having gearing defining at least first, second, third and fourth forward-driving overall ratios in torque flow paths between a throttle controlled engine and a torque output shaft comprising a first gear unit with at least three forward driving ratios and a second gear unit with at least two forward driving ratios, said gear units being disposed in series relationship in said torque flow paths, said torque flow paths including a torque converter with an impeller driven by said engine and a turbine connected drivably to said second gear unit;

• pressure operated clutch and brake means for establishing and disestablishing ratio changes in said gearing including a friction clutch connecting selective two torque delivery elements of said first gear unit to establish a ratio of unity for said first gear unit, first reaction brake means for anchoring a reaction element of said first gear unit during operation in an intermediate ratio of said first gear unit and a second reaction brake means for anchoring a reaction element of said second gear unit during operation in the higher of said two forward driving ratios of said second gear unit;
• said first reaction brake means including a first brake servo having a first servo piston and brake release and apply pressure chambers on opposite sides of said first servo piston;
• said second reaction brake means including a second brake servo having a second servo piston and brake release and apply pressure chambers on opposite sides of said second brake servo piston;
• a control valve system for controlling distribution of pressure to said clutch and brake means including said friction clutch, said apply pressure chambers for said first and second brake servos and said release pressure chamber for said second brake servo, said valve system including a source of line pressure and a main pressure regulator valve means for regulating said line pressure;
• electronic pressure control means communicating with said main pressure regulator valve means for establishing a control pressure determined by operating variables including vehicle speed, turbine speed and engine throttle position, an electronic control pressure passage communicating with said electronic pressure control means;
• first pressure modulator valve means in said control valve system for establishing a first modulated control pressure including a pressure area in communication with said electronic control pressure passage;
• second pressure modulator valve means in said control system for establishing a second modulated control pressure;
• said valve system including ratio shift control valve means for providing controlled communication between said apply pressure chambers of said first and second brake servos and said first pressure modulator valve means and between said release pressure chamber of said second brake servo and said second pressure modulator valve means, said ratio shift control valve means providing also selective distribution of said line pressure to said friction clutch during operation of said first gear unit in the highest of said three forward driving ratios therefor, whereby application and release of said first and second reaction brake means and application of said friction clutch are controlled independently, one with respect to the other, to effect smooth ratio downshifts from said fourth forward driving overall ratio to said second forward driving overall ratio.