Components
Components
The transmission consists of the following:
^ Transmission case (front and rear half)
^ Transmission shafts
^ Gear sets
^ Gear synchronizers
^ Shift mechanism and the engine-side components:
^ Dual-mass flywheel (ZMS)
^ Clutch
Transmission Case
The casing is manufactured from diecast aluminium and flanged mounted with aluminium bolts to the engine block (arrows).
The front half of the casing is also bolted to the rear half with aluminium bolts. The casing is secured at the rear with 4 bolts to the damping block.
Note: Refer to TIS for correct tightening torque, For additional and updated information, refer to the Repair Instructions.
The bolted damping block (1) increases the transmission application for different vehicles. Modifying the acoustic damping to different vehicle types is achieved by changing the damping block.
Dual-mass Flywheel (ZMS)
A specially developed dual-mass flywheel is used with the H-gearbox. Because the 6-speed manual transmission has more gears, the flywheel is modified to compensate for vibration and noise.
In this flywheel, the 2 masses are connected via inner and outer dampers (rubber like damping material).
The masses are now supported by a plain bearing (no longer in a ball bearing). The plain bearing requires less space and enables an additional inner damper to be used.
The transmission input shaft is supported through the flywheel in a needle bushing with a roller pilot bearing. The flywheel is connected to the crankshaft flange with Torx socket bolts.
Clutch: 03/2003 will introduce new heavy metal-free friction linings which satisfy the requirements of used car regulations.
Input Shaft
The input shaft is approximately 25 mm shorter than that in the 5-speed. The input shaft longitudinal splines have an involute shape.
Involute Toothing: This denotes the special shape (mathematical curve) of the toothed segments of the input shaft splines (22 teeth total).
This creates linear contact (dots shown to the right) with the toothed segments to the clutch drive plate center splines. The reduced friction of the linear contact provides easier declutching operation.
The splined clutch drive plate hub and guide sleeve form a seal to decrease contamination of the input shaft. The involute shaped splines make it easier to remove and install the transmission.
Transmission Shift Mechanism
The short shift travel of the (E85) Z4 gearshift handle required a modification to the selector forces of the internal gearshift mechanism. This changed the internal shift gate and shift gate finger. The shift gate finger is permanently attached to the selector shaft and engages the shift gate. The shift gate and finger precisely guide the selector shaft, conveying a precise gearshift sensation to the driver.This also provides a passive lock which prevents 2 gears from being simultaneously engaged.
The gears are shifted by selector forks. The design dictates that the selector fork for 1st and 2nd gears is transmitted as follows: When the selector shaft is pushed forwards (engagement of 1st gear), the selector fork forced is multiplied as it moves backwards to engage 1st gear.
The chamfered shift gate precisely guides diagonal gearshifts (2nd to 3rd, 4th to 5th and vice-versa).
A further function of the shift gate and the shift gate finger is to absorb misuse forces created by the driver at the gearshift lever (previously transmitted via the selector shaft to the selector forks). A reduction of selector forces is achieved by low pretension springs at the 5/6 gutter, reverse gear and � gutter (helical coiled spring).
Note: A correctly operating selector force mechanism ensures that the gearshift lever is without play in neutral.
Transmission Gear Sets
The GS6-37BZ is designed for 5th gear to be direct and 6th gear as an overdrive.
Gear Synchronizers
A triple-taper synchronizer is installed for 1st and 2nd gears. A double-taper synchronizer unit is installed for 3rd and 4th gears. A single-taper synchronizer unit is installed for 5th, 6th and reverse gear.