308-03D Manual Transmission-Transaxle - Vehicles With: 6-Speed Manual Transmission (MMT6) (Manual Transmission): Description and Operation

Construction features on the differential side

All gears have helical teeth and are permanently engaged.

5th, 6th and reverse gear have simple synchronisation. 1st to 4th gears are double synchronised.

Construction features on the input shaft side.

All driving gear wheels of the transmission are located on the input shaft.

The input shaft is a solid shaft and runs on one ball bearing and one roller bearing.

Because of this mounting the input shafts runs without preload and therefore needs no adjusting shims.

The input shaft seal nearest the clutch is pressed into the clutch housing.

Input shaft

Input shaft

The gear wheels for 1st and 2nd gear are an integral part of the input shaft. The gearwheels for 3rd and 5th gears and the gearwheel for 4th/6th gear are pressed on.

Because of the high force used to press on the components, the gear wheels cannot be pressed off in service. A faulty input shaft can only be replaced as a complete unit.

Defective bearings can be pressed off and changed.

Output shaft 1st/4th gear

The 1st/4th gear output shaft runs on tapered roller bearings.

This bearing arrangement requires the shaft to be preloaded. Please refer to the service literature for further information on how to measure the pre-load.

The output pinion of the 1st/4th gear output shaft is an integral part of the shaft.

The synchroniser assemblies of the 1st/2nd and the 3rd/4th gears are located on the output shaft.

The 1st to 4th gear output shaft is a hollow shaft; the oil is supplied to the internal oilways via oil funnels.

Internal oilways provide lubrication to the needle roller bearings and the synchroniser assemblies.

Output shaft 5th/6th/reverse gear

The 5th/6th/reverse gear output shaft runs on tapered roller bearings.

This bearing arrangement requires the shaft to be preloaded. Please refer to the service literature for further information on how to measure the pre-load.

The output pinion is an integral part of the shaft.

The 5th/6th and reverse gear synchronizer assemblies are located on the shaft.

The 5th/6th/reverse gear output shaft is a hollow shaft; the oil is supplied to the internal oilways via oil funnels.

Internal oil passages provide lubrication to the needle roller bearings and the synchronizer assemblies.

Oil funnel and oil storage ring

Until 10/2005 an oil storage ring was installed on the clutch side in each of the two output shafts.

When installing a new oil funnel, from 11/2005 onwards, an oil storage ring is no longer permitted, as this could lead to a loss of transmission fluid pressure in the output shaft and therefore to a loss of lubrication.

Synchroniser assembly

The (MMT6) synchroniser assemblies have been reworked for the 6-speed manual transmission.

The detent balls, springs and sliding blocks form one unit.

This arrangement makes it easier to service the synchroniser assembly.

Differential

Because the Vehicle Speed Sensor (VSS) is discontinued, so is the sender wheel.

The ABS wheel speed sensors send the current wheel speed to the powertrain control module (PCM).

The differential has taper roller bearings.

This bearing arrangement requires the shaft to be preloaded. Please refer to the service literature for further information on how to measure the pre-load.

Power transmission in the individual gears

The following diagrams show a schematic representation of the power flow.

Power is transmitted via the non-positive gear pair to the output pinion of the output shaft(s) and thus to the differential ring gear.

NOTE:The three shafts are shown away from their real positions for clarity.

Power transmission route in 1st gear

The 1st gear wheel is positively connected to the 1st to 4th gear output shaft by the 1st/2nd gear synchroniser assembly.

Power transmission route in second gear

The 2nd gear wheel is positively connected to the 1st to 4th gear output shaft by the 1st/2nd gear synchroniser assembly.

Power transmission route in 3rd gear

The 3rd gear wheel is positively connected to the 1st to 4th gear output shaft by the 3rd/4th gear synchroniser assembly.

Power transmission route in 4th gear

The 4th gear wheel is positively connected to the 1st to 4th gear output shaft by the 3rd/4th gear synchroniser assembly.

Power transmission route in 5th gear

The 5th gear wheel is positively connected to the 5th/6th/reverse gear output shaft by the 5th/6th gear synchroniser assembly.

Power transmission route in 6th gear

The gear wheel of the 4th/6th gear drives not only the gear wheel of the 4th gear but also of the 6th gear.

The 6th gear wheel is positively connected to the 5th/6th/reverse gear output shaft by the 5th/6th gear synchroniser assembly.

Power transmission route in reverse gear

The reverse gear idler is welded to the 1st gear wheel. It is constantly engaged with the reverse gear wheel (shown separated for clarity).

The reverse gear wheel is positively connected to the 5th/6th/reverse gear output shaft by the reverse gear synchroniser assembly.

Internal shift mechanism

Internal shift mechanism

The internal shift mechanism has been newly developed for this transmission.

The reverse gear switch is located on the housing cover of the internal shift mechanism.

The counterbalance improves the smoothness of the gear shifting. Due to its mass, the synchronization shift resistances that can be felt during shifting are reduced. The gear shifting process becomes smoother.

The internal shift mechanism can only be changed as a complete unit in service.