Transmission General Description 5L40-E/5L50-E
The Hydra-matic 5L40-E is a fully automatic, five speed, rear wheel drive, electronically controlled transmission. It consists primarily of a four-element torque converter, one planetary gear set, friction and mechanical clutches and a hydraulic pressurization and control system.
The TCM commands shift solenoids, within the transmission, on and off to control shift timing. The TCM controls shift feel through the pressure control solenoid. The TCM also controls the apply and release of the torque converter clutch which allows the engine to deliver the maximum fuel efficiency without sacrificing vehicle performance. The hydraulic system primarily consists of a vane type pump, two control valve bodies, two channel plates, converter housing and case. The pump maintains the working pressures needed to stroke the clutch pistons that apply or release the friction components. These friction components, when applied or released, support the automatic shifting qualities of the transmission. The friction components used in this transmission consist of nine multiple disc clutches. The multiple disc clutches combine with four mechanical sprag clutches, to deliver six different gear ratios through the gear set. The gear set then transfers torque through the output shaft.
The transmission can be operated in any one of the seven different modes.
| • | P - Park position enables the engine to be started while preventing the vehicle from rolling either forward or backward. For safety reasons, the vehicle parking brake should be used in addition to the transmission Park position. Since the output shaft is mechanically locked to the case through the parking pawl and rear internal gear, Park position should not be selected until the vehicle has come to a complete stop. |
| • | R - Reverse enables the vehicle to be operated in a rearward direction. |
| • | N - Neutral position enables the engine to start and operate without driving the vehicle. If necessary, this position should be selected to restart the engine while the vehicle is moving. |
| • | OD - Overdrive range should be used for all normal driving conditions for maximum efficiency and fuel economy. Overdrive range allows the transmission to operate in each of the five forward gear ratios. Downshifts to a lower gear, or higher gear ratio are available for safe passing by depressing the accelerator or by manually selecting a lower gear with the shift selector. |
| • | 4 - Manual Fourth can be used for conditions where it may be desirable to use only four gear ratios. These conditions include towing a trailer and driving on hilly terrain as described above. This range is also helpful for engine braking when descending slight grades. Upshifts and downshifts are the same as in Overdrive range for first, second, third and fourth gears except that the transmission will not shift into fifth gear. Manual Fourth can be selected at any vehicle speed but will downshift into fourth gear only if vehicle speed is low enough not to overrev the engine, calibratable in TCM. |
| • | 3 - Manual Third adds more performance for congested traffic and hilly terrain. It has the same starting ratio, first gear, as Manual Fourth but prevents the transmission from shifting above Third gear. Thus, Manual Third can be used to retain third gear for acceleration and engine braking as desired. Manual Third can be selected at any vehicle speed but will downshift into third gear only if vehicle speed is low enough not to overrev the engine, calibratable in TCM. |
| • | 2 - Manual Second adds more performance for congested traffic and hilly terrain. It has the same starting ratio, first gear, as Manual Third but prevents the transmission from shifting above second gear. Thus, Manual Second can be used to retain second gear for acceleration and engine braking as desired. Manual Second can be selected at any vehicle speed but will downshift into second gear only if vehicle speed is low enough not to overrev the engine, calibratable in TCM. |
When the vehicle speed slows down to a speed low enough not to overrev the engine, calibratable in TCM, the transmission will automatically downshift into first gear. This is particularly beneficial for maintaining maximum engine braking when descending steep grades.
