Bearing failure on the M32 gearbox is very common.
Typically you will notice a whining noise when cruising on the motorway in 6th gear. The whining will come and go as you press and release the accelerator. When the bearings wear even more, the gearstick will begin to move as you press/release the clutch in first gear.
My own experience indicates that just one bearing fails
Failed bearing is at the top of the photo
Excessive play and loose rollers
Bearing becomes pitted due to metal fatigue
Replacement of this bearing, will usually rectify the issues with gearstick movement and whining.
Background information on the M32 gearbox
- The M32-6 is a 6-speed manual transmission. This transmission is being used for the first time in the Astra-H in conjunction with the Z 20 LEL DOHC II turbocharged petrol engine. This manual transmission is an all-synchromesh 3-shaft transmission.
This 3-shaft transmission has the following advantages:
- Compact construction
- Improved smooth-running performance
- Better shift quality
- High torque transmission
- Low weight
Structure of the manual transmission
Location of the shafts
The following cross-sectional diagram shows the location of the respective shafts in the M32-6 transmission, as per the 3-shaft principle.
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In this transmission angular cone bearings are used for all shafts. These bearings require a certain amount of play and pretension. The required amount of bearing play and pretension is achieved at the production stage by using shims under the angular cone bearing in the transmission housing.
Location of gearwheels
This diagram shows the location of the gearwheels on the respective shaft.
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One particular advantage of this 3-shaft transmission is that on the input shaft, the 3rd gear gearwheel is also used for 5th gear.
Power flow in the individual gears
The following diagrams show the flow of power in the individual gears.
1st Gear
2nd Gear
3rd Gear
4th Gear
5th Gear
6th Gear
Reverse
Location of components in the M32-6 transmission
The following exploded diagram shows the location of the components in the M32-6 manual transmission. The components of the individual shafts will then be described.
| 1 | Axle shaft seal ring | 6 | Axle shaft seal ring |
| 2 | Guide sleeve – differential housing | 7 | Shim |
| 3 | Differential housing | 8 | Differential assembly |
| 4 | Seal ring – axle shaft seal ring sealing flange | 9 | Transmission housing |
| 5 | Axle shaft seal ring sealing flange |
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Location of components in upper main shaft assembly
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Location of components – lower main shaft assembly
| 1 | Thrust piece | 19 | 6th gear gearwheel (driven) |
| 2 | Retaining ring | 20 | Needle roller bearing – 6th gear |
| 3 | 1st/2nd gear shift sleeve | 21 | Roller bearing – main shaft |
| 4 | Outer synchro ring | 22 | Shim |
| 5 | Intermediate ring | 23 | 5th/6th gear shift fork |
| 6 | Inner synchro ring | 24 | Gear shift shaft |
| 7 | 2nd gear gearwheel (driven) | 25 | 1st/2nd gear shift fork |
| 8 | Needle roller bearing – 2nd gear gearwheel | 26 | Synchroniser body |
| 9 | Locking ring | 27 | Outer synchro ring |
| 10 | Pressure piece | 28 | Intermediate ring |
| 11 | 5th gear gearwheel (driven) | 29 | Inner synchro ring |
| 12 | Needle roller bearing – 2nd gear gearwheel | 30 | 1st gear gearwheel (driven) |
| 13 | Synchro ring | 31 | Needle roller bearing – 1st gear gearwheel |
| 14 | Thrust piece | 32 | Retaining ring |
| 15 | Synchroniser body | 33 | Roller bearing – main shaft |
| 16 | Retaining ring | 34 | Main shaft |
| 17 | 5th/6th gear shift sleeve | 35 | Fluid collector pipe |
| 18 | Synchro ring |
Location of components – input shaft assembly
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Synchronisation
An improved synchronisation system, already fitted to the F40 manual transmission, is used on the M32-6 transmission. The previous sliding blocks and synchro springs have been dispensed with and have been replaced with thrust pieces.
Matched synchronisation systems are also used for the individual gears.
Two and three-cone synchronisation systems are used.
The synchronisation systems used for each respective gear will be shown in the following.
1st/2nd gearThe three-cone synchronisation system is used for these two gears.
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3rd/4th gear
A two-cone synchronisation system is used for these two gears.
| 1. | Intermediate ring | ||
| 2. | Synchro ring | ||
| 3. | Shift sleeve | ||
| 4. | Synchroniser body | ||
5th/6th gear
A single-cone synchronisation system is used for these two gears.
1. Synchro ring
2. Shift sleeve
3. Synchroniser body
Reverse gear
Like 5th/6th gear, reverse gear also features a single-cone synchronisation system.
Gearshifting
The M32-6 manual transmission also has a cable gearshift. The individual gears are selected by means of a central gearshift unit.
Mark for the M32-6 manual transmission
The mark for the M32-6 manual transmission consists of a bar code and a combination of numbers.
The letters and numbers located below the bar code have the following meanings:
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Transmission fluid
The M32-6 manual transmission uses the same transmission fluid as the F13 / F17 / F17+ / F23 / F25 / F35 and F40 transmissions.
The transmission’s fluid fill quantity is 2.4 litres.
| Container size | Catalogue number | Part number |
|---|---|---|
| 1 litre SAE 80 | 19 40 768 | 9 120 541 |
| 60 litres SAE 80 | 19 40 710 | 9 194 349 |
Technical data
The maximum input torque for the M32-6 manual transmission is 320 Nm.
The weight of the M32-6 manual transmission is approx. 41.5 kg without fluid.
The overall length of the transmission is 329.5 mm.
Transmission ratio
| Engine | Z 20 LEL |
|---|---|
| 1st gear | 3.818 |
| 2nd gear | 2.053 |
| 3rd gear | 1.302 |
| 4th gear | 0.935 |
| 5th gear | 0.744 |
| 6th gear | 0.614 |
| Reverse gear | 3.727 |
| Output ratio | 3.94 |
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