Volvo M90 transmission
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M90 is the model designation for an automotive rear-wheel drive gearbox that is found in Volvo 940/960 models from 1994-on.
The gearbox is made by Getrag in Sweden and it is of a 3-axle design, deriving from the Volvo M56 gearbox of the front wheel driven 850 series. It is rumored that the gears between these gearboxes can be swapped.
There are three variations of the gearbox. There is a version for the cast iron 4 cylinder engines of the 940 (redblock), the all aluminium 6 cylinder of the 960 (whiteblock), and the version for the Volkswagen 6 cylinder diesel engine D24TIC. The differences are the bell housing bolt pattern and the output shaft flange with a 3-bolt flange for the redblock/diesel engines and a 4 bolt flange for whiteblock engines. The variant for the 6 cylinder Volvo engine will fit on all 4/5/6 all aluminum Volvo N/RN-series engines.
The clutch is hydraulically operated by a master/slave cylinder setup with a normal clutch fork and throw out bearing. The flywheels used with these gearboxes are dual mass versions (petrol engines) to eliminate the noise that 3-axle (3-shift) gearboxes can make in neutral, and a regular (single mass) flywheels for the diesel engine.
All gears, including the reverse gear, are synchronized.
The M90 gearbox is available with different gear ratios.
| Gear | M90H1 | M90H2 | M90L1 | M90L2 |
|---|---|---|---|---|
| 1 | 3.54:1 | 3.54:1 | 3.91:1 | 3.91:1 |
| 2 | 2.05:1 | 2.05:1 | 2.20:1 | 2.20:1 |
| 3 | 1.38:1 | 1.38:1 | 1.38:1 | 1.38:1 |
| 4 | 1.00:1 | 1.00:1 | 1.00:1 | 1.00:1 |
| 5 | 0.81:1 | 0.70:1 | 0.81:1 | 0.70:1 |
This gearbox is the strongest manual transmission that Volvo fitted to their rear wheel drive cars. The H versions are stronger than the L versions.
The later versions are better, Volvo redesigned the 3rd gear synchronizer in 1997 to eliminate the possible failure of the synchronizer due to bad gear engagement under heavy loads. It is possible to modify the synchronizer of the older M90 gearboxes to eliminate the problem.
