Manual Transmission/Transaxle: Description and Operation
Manual Transmissions
MINI COOPER
The manual transmission and final drive assembly installed in the MINI COOPER is known as the R65. This transmission has 5 forward speeds and a maximum torque input of 160 Nm. The shift pattern is of a conventional design with reverse gear opposite 5th gear, and neutral in the 3rd/4th gear plane.
Features of the R65 Transmission assembly include:
- Two Shaft Design
- Input shaft incorporating four fixed input gears and 5th gear located by splines and a lock nut
- All output gears free to rotate on the output shaft
- Overall length of just 395mm including the clutch housing
- All forward gears have synchromesh with dual cone synchromesh on 1st , 2nd and 3rd gears
- Aluminum die cast housings with the exception of the rear cover that is pressed steel
- All housings are sealed with liquid sealer except the rear housing that has a rubber seal
Primary components of the R65 transmission are:
- Gears and Shafts
- Clutch Housing
- Main Housing
- Shift Mechanism
System Components
Gears and Shafts
The gear tooth design has been optimized for gearbox smoothness and efficiency. The fine tooth design allows more teeth to be in mesh with each other at any moment. There will be three teeth in mesh as opposed to two in conventional gearboxes. This greatly reduces gear noise.
The input shaft incorporates fixed 1 st, 2nd , 3rd and 4th speed input gears forming a single component. 5th gear is spline to the input shaft and secured with a lock nut. The output shaft assembly contains all free rotating output gears and synchronizer assemblies.
The differential is mounted on two tapered roller bearings. The need to take pre-load measurements is negated by the use of very close machining tolerances on the various components. This accuracy is achieved with a new machining technique that employs the very latest technological advances. Automated machines take temperature readings from the aluminum block being machined, the cutting head and cutting fluid and make necessary adjustments to compensate for temperature fluctuations.
Clutch Housing
The clutch housing is bolted and doweled to the rear of the engine. It houses the flywheel, clutch, clutch release fork, clutch release bearing guide and input shaft seal. It also provides space for the differential, a differential bearing, and a seal housing for the right hand drive shaft.
Main Housing
The Main Housing houses the gearbox breather, reverse light switch, selector shafts, input shaft and output shaft, all gears except 5th and the reverse gear idler shaft.
The intermediate plate assembly is situated on the gearbox side of the clutch housing. It provides support for the gear selector lever and input and output shaft bearings.
Rear Cover
The rear cover is an extension to the Main Housing providing a housing for 5th gear, 5th gear synchromesh hub and the selector fork. The rear cover also houses an oil trap and guide to supply oil to the hole inside the output shaft. Cross drilled holes in the shaft provide lubrication for the gears.
Shift Mechanism
Principle of Operation
The input shaft incorporates fixed 1 st , 2nd , 3rd and 4th speed input gears forming a single component. 5th gear is spline to the input shaft and secured with a lock nut. The output shaft assembly contains all free rotating output gears and synchronizer assemblies.
First Gear
The first gear synchromesh hub is fixed to the output shaft. The synchromesh cones synchronize the speed of first gear on the output shaft to the speed of the input shaft. The hub then locks first gear to the output shaft and drive is transmitted.
Second Gear
The second gear synchromesh hub is fixed to the output shaft. The synchromesh cones synchronize the speed of second gear on the output shaft to the speed of the input shaft. The hub then locks second gear to the output shaft and drive is transmitted.
Third Gear
The third gear synchromesh hub is fixed to the output shaft. The synchromesh cones synchronize the speed of third gear on the output shaft to the speed of the input shaft. The hub then locks third gear to the output shaft and drive is transmitted.
Fourth Gear
The fourth gear synchromesh hub is fixed to the output shaft. The synchromesh cones synchronize the speed of fourth gear on the output shaft to the speed of the input shaft. The hub then locks fourth gear to the output shaft and drive is transmitted.
Fifth Gear
The fifth gear synchromesh hub is fixed to the output shaft. The synchromesh cones synchronize the speed of fifth gear on the output shaft to the speed of the input shaft. The hub then locks fifth gear to the output shaft and drive is transmitted.
Reverse Gear
Reverse gear is incorporated into the 1 st and 2nd gear hub, which is fixed to the output shaft. When reverse gear is selected the 1st and 2nd selector shaft is moved, a fixed arm on the shaft interlocks with the reverse gear arm, moving the gear into mesh with the fixed hub.
Note:
1 st and 2nd selector fork does not move during reverse engagement.
An interlock mechanism includes an inhibitor to physically prevent reverse gear from being inadvertently selected directly from 5th gear.
Service Information R65
The oil drain and filler level plugs on the R65 gearbox are both positioned in the differential housing on the main gearbox housing. Both plugs have an external hexagonal 17 mm head.
With the vehicle on level ground, the gearbox is filled until the oil is level with the bottom of the filler/level plug hole.
There is no requirement for maintenance at any of the service intervals.
Oil type MTF 94 (fill for life) capacity (service fill) 2 liters.
Drain plug torque 32-40 Nm
Filler plug torque 20-30 Nm
Gearbox housing to clutch housing Loctite 5900 sealer.
Clutch housing to intermediate plate Loctite 549 sealer.