The GM400 gearbox of the Silver Shadow:

Technical information





Animation of the GM400 gearbox

1. Torque Convertor
2. Forward Clutch
3. Direct Clutch
4. Front Band
5. Intermediate Sprag
6. Intermediate Clutch
7. Rear Sprag
8. Rear Band
9.   Intake Filter
10. Heat Exchanger
11. Restrictor & Check Ball Valve
12. Front Servo
13. Rear Servo
14. Governer
15. Pump
16. Input Shaft
17. Pressure Regulator & Boost Valve
18. Manual Valve
19. Gear Indicator
20. Output Shaft
21. Oil Strainer & Sump
22. Detent Valve
23. Regulator Valve
24. 1-2 Valve
25. 1-2 Detent Valve
26. Regulator Plug
27. VacuŁm Modulator
28. Modulator Valve
29. Detent Solenoid
30. 1-2 Accumulator Valve
31. 2-3 Valve
32. 2-3 Modulator Valve
33. 3-2 Valve

The following drawing reveals a lay-out of all hydraulic components such as the torque convertor, the fluid pump, the servos and clutches, the external heat exchanger, the detent solenoid and all valves of the valve regulator box.

The animation shows all different stages of the GM400 gearbox, each stage for approximately 3 seconds. All components are operated by the gear lever in the centre of the animation, component number 19. When a gear is selected, all valves and parts move in the correct position. When 'Drive' ('D') is selected with the gear lever, the animation shows how the gearbox upshifts from the first to the second and third gear.
When 'Park' ('P') is selected with the gear lever (19), the outgoing shaft (20) is mechanically locked, keeping the vehicle stationary, even while the engine is not running.
The next position is 'Reverse' ('R'). The mechanical park position is now released and (while the engine is running) the internal fluid pump will produce a rising fluid pressure in the valve regulator box, activating the rear servo. Then the drum of the rear planetary gear will be locked, resulting in reversing the rotation of the output shaft, illustrated as the clockwise direction of the arrow.
The next position is 'Neutral' ('N'), that is identical to 'Park' except for the lock of the output shaft. Now the car can be moved freely forwards and backwards, even when the engine is not running.
The next position is 'Drive' ('D'). In this position of the gear lever all three forward gears can be selected automatically, depending on the speed of the car, the torque demand, the throttle position and kick-down position. The kick-down position operates an internal 'detent-solenoid' that alters the hydraulic pressure in some parts of the valve regulator box. As a result, the gearbox shifts from third to second or from second to first gear.
The last positions of the gear lever are 'Intermediate' ('I') and 'Low Range' ('L'). In the 'I' position the gearbox will only select the first two gears and can be used to climb steep hills. If the 'L' position is selected the gearbox will stay in the first gear. The 'L' position can be used for pulling heavy loads or ascending steep hills.


© Marinus Rijkers.   Disclaimer