Design

Design

Transmission general




M66 is a six gear manual transmission. All gears, including back-up (reverse), are synchronized. The transmission is intended to be part of a transverse drive line with front wheel or four wheel drive.
The transmission is built together with the final driven in a common aluminum housing. This unique construction makes the transmission very compact while enabling it to transmit high torque.
The engine and transmission have damped mountings, either on the side members with pendulum mounting or on a sub frame.
The transmission and final drive are extremely compact. For further information about dimensions, see Specifications, transmission.
The oil is synthetic and does not normally need to be changed. The oil is heat resistant and tolerates high loads. The hole in the level plug is used to top up the oil and check its level. The oil is drained through the drain plug in the base of the transmission.
The gear wheels are located on four shafts. They are:
- input shaft (A)
- intermediate shaft 1-2, 5-6 (B)
- intermediate shaft 3-4 (C)
- back-up (reverse) shaft (D).
The clutch gears are welded directly to the idler wheel to shorten the length of the shaft. To further shorten the length of the transmission, needle bearing with inner rings are used instead of snap rings.
The inner rings sit on the shaft inside the idler gears and extend lengthwise a little outside each idler gear. When the components on the shafts are pulled together the inner rings counterhold, so that the idler wheels have the clearance that they require to rotate.
The components of the input shafts are pulled together with a bolt located in the end of the shaft. Components of intermediate shaft 3-4 are held together with a press joint and a bolt located in the end of the shaft. The components of intermediate shaft 1-2, 5-6 are held together with the press joint of the 5th and 6th gear pinion.

Transmission, internal components










Gear selector, internal









The gear selector is in a single complete unit with the exception of the ball limiter for the gear position. This is threaded in the transmission housing. The gear selector is held in position by 4 screws. 2 guide pins in the control housing and a needle bearing in the bottom of the gear selector unit control the position in the transmission housing.
Back-up (reverse) gear in the gear selector assembly is furthest to the right and down. Neutral is between 3rd and 4th.
The back-up (reversing) lamp switch is in the control housing and is affected by the shaft for lateral movement. The back-up (reversing) lamp switch is directly connected to the central electronic module (CEM).
The gear selector unit must not be dismantled. In the event of a fault the whole gear selector unit must be replaced.
4 gear selector forks transfer the movement from the control to the relevant coupling sleeve.

Gear selector assembly and mechanical transmission cables




1. Locking the adjustable mechanical transmission cable for lateral travel
2. Solenoid
3. Gear selector assembly
4. Mechanical cables
5. Mechanical cables bracket.
The mechanical cables are in a cable assembly. In the event of a fault or damage with any of these the whole mechanical cable assembly must be replaced.
The cable sleeves are secured using quick connectors in the gearshift assembly and in the cable bracket on the transmission.
The mechanical transmission cable for lateral travel is adjustable lengthwise. The adjuster is positioned on the mounting towards the lever on the transmission (1).
The gear selector assembly is made of plastic. It has rubber feet (to reduce noise and vibration).
The gear selector assembly has a lever and a lever arm. There is a return spring on the lateral movement lever.

Back-up (reverse) inhibitor
The shift lever assembly houses a solenoid that serves as an electronically controlled reverse inhibitor.
There is an electronic damping function on the solenoid which gives the solenoid a soft action. This reduces noise. The solenoid can be replaced.

Differential




The differential distributes drive shaft torque equally between the drive wheels, even if they are rotating at different speeds.
The differential consists of the differential housing, large and small side gears, shaft journals and thrust washers.

Applies to AWD
On the M66 AWD a sleeve for power transfer is located on the differential.

Synchronization
The synchronizing hub assembly consists of a coupling sleeve, flange and the hub. Each synchronizing hub is joined to its shaft by splines and rotates with it.
There are idler wheels on both sides of each synchronizing hub. The idler wheels rotate freely on the shaft (does not apply to reverse gear). Each idler wheel is constantly engaged in its pinion. The synchronizing set is positioned between the synchronizing hub and the idler wheel.
The synchronizing units are positioned on the shafts in the transmission as follows:
- The synchronizing unit for 1st - 2nd gear is on the intermediate shaft 1-2, 5-6
- The synchronizing unit for 3rd - 4th gear is on the intermediate shaft 3-4
- 5th-6th the synchronizing unit is on the input shaft
- the synchronizing unit for back-up (reverse) gear is on the back-up (reverse) shaft.
The synchronizing rings expand when heated by the same amount as the components they are in contact with. As a result no safety margin is required to counter expansion.
The idler wheels for single and double synchronization have no cones. An inner ring on the synchronizer unit performs this function instead.
The synchronizer unit is a modular system. This makes it easy to upgrade from a single synchronizer to double synchronization by replacing the synchronizer kit.




Single synchronization, which has one friction surface, is on:
- back-up (reverse) gear
- 4th gear
- 5th gear
- 6th gear.
The outer ring (to the left in the illustration) is manufactured in pressed steel. The inner ring is pressed steel and the friction surface is coated with sintered brass.




Double synchronization, two friction surfaces, is on:
- 3rd gear.
The outer ring (to the left in the illustration) is manufactured in pressed steel. The sealing ring is pressed steel and the friction surfaces are coated with sintered brass. The inner ring is machined steel.




Triple synchronization, three friction surfaces, is on:
- 1st gear
- 2nd gear.
The outer ring (left in the illustration) is made of pressed metal. The intermediate ring is made of pressed metal with a sintered brass coating on the friction surfaces. The inner ring is of pressed metal with a sintered brass coating on the inner friction surface. Triple synchronization also includes a ring integrated with the idler wheel.

Clutch, general




The main task of the clutch system is to transfer torque, disengage during shifting, allow comfortable starting and to act as an efficient vibration damper to eliminate noise and vibration in the chassis and drive train.
The clutch is located between the engine and the transmission. The main components are a pressure plate and a clutch driven plate. The clutch is used to connect the torque from the engine to and from the transmission and therefore to drive the wheels.
The clutch is a single disc dry clutch. The clutch disc is connected to the transmission input shaft on the transmission.
On vehicles with more powerful engines, self-adjusting clutches are used to lower the engagement forces.

Hydraulic clutch control mechanism with concentric slave cylinder (CSC)




The clutch control mechanism is fully hydraulic. The slave cylinder is inside the clutch cover. There is no mechanical transfer (fork) inside the clutch cover from an external slave cylinder.
The concentric slave cylinder (CSC) means that the slave cylinder is integrated with the throwout bearing.
The concentric slave cylinder (CSC) is extremely efficient and reliable and the throwout bearing is accurately centered.
The unit is mounted with a bolt in the gearcase. The bearings and sliding surfaces do not require lubrication. The bearing on the concentric slave cylinder is self-centering to the clutch fan.
The hydraulic line from the master cylinder is connected to the concentric slave cylinder (CSC) via an adapter. There is a bleed nipple on the adapter.
There are ratios built-in to the system to reduce the force required to transfer torque:
- pedal effort
- hydraulic force
- clutch finger force.
The force is reduced from approximately 8600 N at the clutch to approximately 100 N at the pedal.
If the clutch pedal returns too quickly, the drive line could be damaged by the high torque. There is a shock load limiter in the clutch to avoid this. The shock load limiter chokes the flow between the concentric slave cylinder (CSC) and the master cylinder if there is a danger of the excessive torque. The shock load limiter is in the concentric slave cylinder.

Shock load limiter




In vehicles with engines with high engine torque the return time of the clutch pedal may be too short. This means that the torque peak is so high that it can damage the driveline.
In the event of the torque peak being to high, the hydraulic flow in the engagement direction is choked between the concentric slave cylinder (CSC) and the master cylinder using a shock load limiter.

Self-adjusting clutch (SAC)




A self-adjusting clutch (SAC) eliminates problems both in terms of wear in the clutch cover and the need for increased force at the pedal as the facing thickness reduces.
This considerably increases the life of the clutch. A self adjusting clutch will not normally require replacement during the lifetime of the vehicle.
A self-adjusting clutch (SAC) senses the increase in release load at the diaphragm spring. It has a adjustment mechanism between the diaphragm spring and the clutch housing. This maintains the position of the diaphragm spring and ensures that the pedal effort required remains constant throughout the service life of the vehicle.
The pressure plate is of the diaphragm spring type. Unlike a traditional type, the pressure plate contains an adjustment ring made of steel or plastic. If there is wear, the adjustment ring moves slightly to maintain the engagement position of the clutch.
The fact that the fingers are unable to move backwards has the following advantages:
- increased wear capacity
- the clutch cover can be made shorter because space is not required for rearward movement of the diaphragm spring.

Clutch driven plate




The clutch driven plate is the component that transfers the torque to the input shaft and into the transmission.
The clutch driven plates of today do not have dampers or friction elements. These functions are integrated in the dual mass flywheel.
The clutch driven plate center is greased internally when the clutch driven plate is installed at the factory. This reduces the friction between the clutch driven plate and the input shaft to make shifting easier.
When replacing the clutch driven plate, the input shaft must be lubricated. See the instructions for replacing the clutch.

Dual mass flywheel




The dual mass flywheel reduces noise from the transmission and improves driveability.
The dual mass flywheel helps reduce the load on the crankshaft bearings. It also improves shift quality because the flywheel mass on the clutch driven plate is lower.
The components of the dual mass flywheel can rotate in relation to one another. This twisting depends on the load from the engine. Twisting of a dual mass flywheel is up to 60 degrees in both directions. You can feel a certain twisting between the components if you turn a dual mass flywheel.