For a view of the oil flow diagram, refer to the 1996 TURM Manual.

To obtain Fourth gear, the PCM receives input signals from the VS Sensor and the TP Sensor in order to energize (turn ON) the supply of current to the 1-2 shift solenoid valve (315). When energized, line pressure is directed into the 1-2 shift solenoid valve passage and on to the 3-4 shift valve (362). Fluid from the 1-2 shift solenoid valve moves the valve against spring pressure. This allows third fluid to enter both the fourth fluid passage and the fourth clutch fluid passage. Fourth fluid seats the #10 checkball (372). The fluid also forces the checkball through a feed orifice in order to stroke the 3-4 accumulator piston (428) while applying the fourth clutch. The 3-4 accumulator fluid on the spring side of the piston is forced through the 3-4 accumulator pin (426) into the 3-4 accumulator passage, and the fluid exhausts at the 3-4 accumulator valve (350).

The 1-2 shift solenoid valve energizes in order to prevent fluid from exhausting out of both the line passage and the 1-2 shift solenoid valve passage.

Spring pressure combines with off fluid pressure from the end of the 2-3 shift solenoid valve in order to hold the 1-2 shift valve against the 1-2 shift solenoid valve.

When shifted against a spring force, the 3-4 shift valve allows third fluid to enter both the fourth fluid passage and the fourth clutch fluid passage. Fourth fluid seats the #10 checkball (372). The fluid is then forced through a feed orifice before stroking the 3-4 accumulator piston (428) and applying the fourth clutch.

The #10 checkball is located in the valve body (300). The checkball forces fourth fluid through a feed orifice into the fourth clutch passage in order to stroke the 3-4 accumulator piston (428).

The 3-4 accumulator piston cushions the application of the fourth clutch by using fourth clutch fluid to stroke the piston against a spring force and also against the 3-4 accumulator fluid.

The 3-4 accumulator valve controls the rate of exhaust of the 3-4 accumulator fluid during fourth clutch application.