There are many different automatic transmissions that are based on the basic Simpson gear train. Most have similar power flows and major components. The primary differences between most of the transmissions is in the nomenclature and holding devices used by the different manufacturers. The following transmissions are presented to illustrate the similarities of all Simpson-based transmissions and to expose you to some of the nomenclature used by the manufacturers.

Nissan Motor Company Transmissions A widely used Nissan RWD transmission is the L4N71B/E4N71B series. These transmissions provide four forward gears through the use of a Simpson gearset and an additional planetary unit mounted in front of the Simpson. The primary difference between the "L" and the "E" is that the E-model provides converter lock-up in third and fourth gear.

These transmissions use four multiple-disc clutches, two servos and bands, and a one-way clutch to provide for the different ranges of gears. The direct clutch is applied in all gears except overdrive. Its purpose is to bypass the overdrive planetary gearset and transfer engine torque to the Simpson gearset. The forward or rear clutch is applied in all forward gears. The high/reverse (front) clutch is applied in reverse gear and third and fourth gears. The low/reverse clutch is applied in reverse and in manual low. This clutch serves as a brake and allows for engine braking during manual low operation. All of these clutches except the low/reverse unit are released by several small coil springs. The low/reverse unit utilizes a belleville-type spring for greater clamping pressures.

The bands and the one-way clutch are used as holding members. The second band is applied only in the second gear. The overdrive band is applied only when the transmission is operating in fourth gear. The one-way clutch is locked during first gear operation but freewheels and is ineffective during deceleration or coasting. The bands are externally adjustable. Refer to the chart below, the clutch and band application chart, for more details on power flow.

Toyota Motors Transmissions Many different transmissions and transaxles have been used by this manufacturer. One of the most common is the A-140E/A-140L, used in Camry and Celica models. This transaxle combines a 3-speed transmission with an overdrive assembly. The A140E is used on Camry and Celica models, whereas the A140L is used on the Celica GT-S. The primary differences between the L and E type transaxles are the main valve body, operating mechanism, and electronic control. The E is referred to an  electronic controlled transaxle (ECT). The ECT is different from the oil pressure control transaxle (A140L) in that it is controlled by a microprocessor located behind the glove box. The A140L uses an electronic overdrive solenoid system.

Although these transaxles are electronically controlled, the basis for operation is a Simpson gear train in line with a single overdrive planetary gearset. The transaxles uses four multiple-disc clutches, two band and servo assemblies, and three one-way clutches to provide the various gear ranges.

Refer to the clutch and band application chart given below for details on the power flow through this transmission.