Getrag F28/6 transmission
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- Clutch diameter: 9.0 inches
- 1st gear ratio: 3.57:1
- 2nd gear ratio: 2.16:1
- 3rd gear ratio: 1.45:1
- 4th gear ratio: 1.10:1
- 5th gear ratio: 0.89:1
- 6th gear ratio: 0.74:1
- Reverse gear ratio: 3.23:1
- Final drive ratio: 3.72:1 (front), 3.70:1 (rear)
There have been many references to the numbering designation that Opel elected to utilise for gearboxes, one of the more common arguments is that it refers to the ft·lbf torque capacity of the gearbox, in this case being a 380 newton metres (280 lbf·ft) torque limit. Other arguments include that it is simply related to the engine size (the F28 gearbox was fitted to a 2.0L turbo engine, with the 1.4 multiplier applied for turbocharged vehicles).
The GM transmissions are usually numerically designated in Newton Metres. For example: The 6-speed M32 gearbox is fitted to the Opel/Vauxhall Astra VXR (pre-J model) and has a torque rating of 320 N·m (240 lb·ft) (hence '32' designation). By no small coincidence the maximum torque output of the Astra VXR engine (Z20LEH) is limited to 320 N·m (240 lb·ft).
The F28/6 in the Calibra was designed to follow a transverse oriented C20LET engine feeding the front wheels with an outlet to facilitate a driveshaft to feed the rear wheels as well. If the four-wheel drive system is disengaged, the gearbox will feed only the front wheels. Conversion kits are readily available from aftermarket suppliers to convert the 6 speed transmission to suit a front-wheel drive vehicle, and this is not an uncommon upgrade (from the 5 speed F20 transmission) amongst owners of the C20XE and X20XEV Calibras.
The nomenclature of the Opel transmissions is as follows:
The letter F stands for "F"ront-wheel-drive. Although the F28 is only used in 4WD applications, the base transmission still remains a common FWD gearbox. The number 28 stands for the maximum torque capacity in Nm/10. 28 means that, the transmission is capable to transfer 280 N·m (210 lb·ft) nominal torque on the input shaft.
Compare: Actual transmission in Opel Signum: F40 means: FWD transmission with torque capacity of 400 N·m (300 lb·ft).
- Courtenay Sport, "Transplants", See Heading F28 to 2WD. Accessed 9 Dec 2006