52 Four speed and reverse longitudinally mounted automatic transmission mechanical power flow

(Similar gear trains are adopted by some ZF, Mercedes-Benz and Nissan transmissions) The epicyclic gear train is comprised of three planetary gear sets, an overdrive gear set, a forward gear set and a reverse gear set. Each gear set consists of an internally toothed outer annular ring gear, a central externally toothed sun gear and a planet carrier which supports three intermediate planet gears. The planet gears are spaced evenly between and around the outer annular gear and the central sun gear.

The input to the planetary gear train is through a torque converter which has a lock-up clutch. Different parts of the gear train can be engaged or released by the application of three multiplate clutches, two band brakes and one first gear one way roller clutch.

Table 5.1 simplifies the clutch and brake engagement sequence for each gear ratio.

A list of key components and abbreviations used are as follows:

1 Manual valve MV

2 Vacuum throttle valve VTV

3 Governor valve GV

4 Pressure regulating valve PRV

5 Torque converter TC

Fig. 5.1 Torque multiplication and transmitted power performance relative to vehicle speed for a typical four speed automatic transmission

9 Converter check valve CCV

10 Drive clutch DC

11 High and reverse multiplate clutch (H + R)C

12 Forward clutch FC

13 Overdrive band brake ODB

14 Second gear band brake 2GB

15 Low and reverse multiplate brake (L + R)B

16 First gear one way roller clutch OWC

17 Torque converter one way clutch OWCR

18 Parking lock PL

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